Modul Chemistry Form 5 [email protected]1 CHAPTER 1 : RATE OF REACTIONS A Rate of Reaction Learning Outcomes You should be able to : state what rate of reaction is identify observable changes to reactants or products for determining rate of reaction determine the average rate of reaction determine the rate of reaction at any given time from a graph solve numerical problems involving average rate of reaction. solve numerical problems involving rate of reaction at any given time. Activity 1 : What is rate of reaction? Rate of reaction is the ……………… at which reactants are converted into .…………………. in a chemical reaction. The rate of reaction is a measurement of the change in the quantity of …………………. or …………………………. against time. Rate of reaction = Change in quantity of reactant /Product Time taken Activity 2 : Fast (F) or Slow (S) reactions? Write F for the fast reaction and S for the slow reaction. 1. Fading of dyes on a shirt under hot sun 6. Striking a match 2. A piece of paper turning yellow 7. Rusting of a water pipe 3. Frying an egg 8. Ripening of tomatoes 4. The weathering of limestone by acid rain 9. Digesting food 5. Burning of petrol in a car engine 10. Cooking a chicken using microwave oven Activity 3 : Observable changes for measuring the rate of reaction The change in amount of reactant / product that can be measured by : …………………………….. in the mass of reactant …………………………….. in mass of product …………………………….. in volume of gas released …………………………….. of precipitate Change in pH, temperature or electrical conductivity
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For each of the reactions below, write a chemical equation and state the observable change/changes can be used as selected quantities to measure the rate of reaction : Example 1 : The reaction between marble chip with hydrochloric acid to produce carbon dioxide gas and chloride salt. Chemical Equation : ………………………………………………………………………………. Changes :
b) Instantaneous rate of reaction (Rate of reaction at any given time)
The rate of reaction at t sec
= gradient of the curve at t sec = a cm3s-1 b
c) Determining the rate of reaction at any given time
Average rate of reaction in the first two minutes = volume of gas collected in the first 120 seconds (cm3) time taken (s) = cm3s-1
Average rate of reaction in the third minute Volume of gas collected in the first 180 sec = V3 Volume of gas collected in the first 120 sec = V2 Volume of gas collected in the third minute = ____________ cm3
Time taken for the reaction = 180 – 120 = _______ s
Average rate of reaction in the third minute = m3s-1
Time (s)
Volume of gas (cm3)
V1
30 120
160
V2
Instantaneous rate of reaction / the rate of reaction at 120 sec = gradient of the curve at 120 sec = cm3s-1
Activity 5 1. The following figure shows the graph of carbon dioxide, CO2 gas produced when an excess of calcium carbonate, CaCO3 reacts with 40 cm3 of 0.1 moldm-3 hydrochloric acid, HCl.
(a) Calculate the
(i) Average rate of reaction in the first 10 sec
(ii) Average rate of reaction in the first 30 sec
(iii) Overall average rate of reaction
(b) Based on the results in (a), how does the rate of reaction change with time. …………………………………………………………………………………………………………………….. (c) Explain your answer in part (b) with respect to the concentration of hydrochloric acid. …………………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………… 2. The following table shows the volume of a gas collected from an experiment.
Calculate th average rate of reaction for (a) the first 60 seconds (b) the overall reaction 3. The decrease in mass of a reaction mixture is recorded in the following table.
Time (min) 0 1 2 3 4 5
Mass of reaction mixture (g) 2.90 1.90 1.25 0.75 0.40 0.10
(a) Draw a graph of mass of reaction mixture against time.
(b) Calculate the rate of reaction at the third minute.
B FACTORS AFFECTING THE RATE OF REACTION
Learning Outcomes
You should be able to :
design experiments to investigate factors affecting the rate of reaction.
give examples of reactions that are affected by size of reactant, concentration, temperature and catalyst.
explain how each factor affects the rate of reaction.
describe how factors affecting the rate of reaction are applied in daily life and in industrial processes.
solve problems involving factors affecting the rate of reaction.
apply knowledge on factors affecting the rate of reaction in everyday activities.
Activity 6 : Factors affecting the rate of reaction. State five factors that affect the rate of reaction : (a) ……………………………………………. (b) …………………………………………..
(c) ……………………………………………. (d) …………………………………………..
(e) …………………………………………….
Activity 7 : Speeding up the Rates of reaction. The following changes may speed up the rate of a chemical reaction between an acid and magnesium. Put a tick in the box next to each one that will speed up the reaction (assume that there is initially an excess of acid) and state the specific factors that affect the reaction.
Statement of factors that affect the rate of reaction Specific factor
Activity 8 : Experiments to investigate the rate of reaction.
(i) Effect of size of reactants Aim : To investigate the effect of size of reactant in an experiment between marbles and hydrochloric acid on the rate of reaction. Equation : ……………………………………………………………………………………………..
The curve of experiment 2 is ……………………………. than experiment 1.
The rate of reaction of experiment 2 is ………………… than experiment 1
The smaller the size of reactants, the …………………………. the total surface area, the …………………………. the rate of reaction.
Aim : To investigate the effect of concentration of sodium thiosulphate solution on the rate of reaction. Equation : …………………………………………………………………………………………………..
* The higher the concentration of the sodium thiosulphate solution, the …………………………… the time taken.
* 1/ t is ………………………………
The …………………. the concentration of sodium thiosulphate solution, the ………………………..the
(iii) Effect of catalyst Aim : To investigate the effect of the presence of catalyst (Manganese (IV) oxide) on the rate of decomposition of hydrogen peroxide. Equation : …………………………………………………………………………………………………….. Draw the apparatus set-up for the experiment.
The curve of experiment 2 is ……………………………………………. than experiment 1.
The rate of reaction of experiment 2 is ………………………………….than experiment 1
The presence of catalyst, will …………………….................... the rate of reaction.
Volume of gas (cm3)
Time (s)
Experiment 1 : with catalyst Experiment 2 : without catalyst
Activity 9 1 2. Meat cut into small pieces, have ……………………….. size compare to the meat cut into big
pieces. The ……………………… the size, the bigger the ……………………………………….
of the meat, hence the …………………………………… the rate of reaction.
3. State and briefly discuss two industrial processes that make use catalyst. [8 marks ] (i) Haber process is a chemical process to produce ……………………………… from nitrogen and
hydrogen gas. The equation of this process is …………………………………………………………...
The suitable condition of reaction are temperature : ………………………………………,
pressure : ………………………………….. and catalyst : ………………………………………………..
(ii) ……………………………… process is a chemical process of synthetisising sulphuric
acid. The equation of stage III for this process is……………………………………………..
The suitable condition of reaction are temperature : ………………………………………,
pressure : …………………………………….. and catalyst : ……………………………………………..
C COLLISION THEORY Learning Outcomes You should be able to :
relate reaction with energy produced by movement and effective collision of particles.
describe activation energy.
sketch and describe energy profile diagram
relate the frequency of effective collisions with the rate of reaction
relate the frequency of effective collisions with factors influencing the rate of reaction
describe how a certain factor affects the collision of particles in a reaction
[ Temperature in refrigerator is ……………………………. The lower temperature caused the bacteria
to be less ………………………. A little …………………… is released by the bacteria. The rate of the
food turns bad is …………………………. ] //
[ Temperature in kitchen cabinet is ………………………. The higher temperature caused the bacteria
to be ……………………reactive. A ………………………… toxic is released by the bacteria. The rate
of the food turns bad is ……………………………….]
Food store in a refrigerator lasts longer than food stored in a kitchen cabinet. Explain why. [4 marks]
One kilogram of meat, cut into big pieces, takes a longer time to cook compared to one kilogram of meat cut into small piece. Explain the above statement based on the size of the particles. [2 marks]
Activity 10 Understandings the Collision Theory 1. What is collision theory ? A theory used to explain chemical reactions in terms of (i) …………………………………………………………………………………………………………………… (ii) ………………………………………………………………………………………………………………….. (iii) …………………………………………………………………………………………………………………. 2. The collision theory states that : (i) A chemical reaction occurs when the reactant particles ……………………….. each other. (ii) Not all collision result in the formation of ………………………………… (iii) A collision is ……………………………. only when the reactant particles have enough energy to overcome the ………………………………………………… of the reaction and when they collide in the proper orientation. 3. What is activation energy ?
The …………………………………… energy which the colliding reactant particles must have that can result a chemical reaction. 4. Energy profile diagram
In the energy profile diagram, the activation energy is the difference in the energy between the energy of the ……………………. and the energy shown by the peak of the curve.
An increase in the concentration of the solution of
a reactant or in the pressure of gaseous reactants
will result in an __________________ in the rate
of reaction. Why? When the concentration of the
solution of a reactant increases, the
_________________ of particles per unit volume
of this reactant also _______________. With more
particles per unit
volume of the solution, the frequency of collisions
per unit time between the reacting particles
__________________. Thus, the frequency of
effective collision ________________ and hence,
the rate of reaction becomes
___________________.
Use the words below to fill in the blank boxes in the diagram Bigger surface area more particles cold hot slow less particles fast bigger size slow smaller size
Activity 13 1. A group of pupils carried out three experiments to investigate the factors affecting the rate of a reaction. Table below shows information about the reactants and the temperature used in each experiment.
Experiment Reactants Temperature / oC
A Excess magnesium ribbons and 25 cm3 of 0.5 mol dm-3 hydrochloric acid
25
B Excess magnesium ribbon and 25 cm3 of 0.5 mol dm-3 hydrochloric acid
35
C Excess magnesium powder and 25 cm3 of 0.5 mol dm-3 hydrochloric acid
35
Sketch a graph of these experiments on the same axes. [4 m] 2.. A student carried out three experiments to investigate the effects of the factors influencing the rate of reaction. Table below shows the results of the experiments.
Experiment I II III
Set-up of apparatus
Temperature / oC 30 40 40
Time taken for all the magnesium to dissolve / s
50
20
15
Sketch the graphs for the volume of hydrogen gas against time for Experiments I, II and III using the same axes.
A UNDERSTANDING CARBON COMPOUND Learning Outcomes You should be able to:
State what carbon compound is,
State the carbon compounds can be classified into two groups, i.e. organic and inorganic,
State what organic compound is,
Gives examples of organic and inorganic carbon compounds,
State what a hydrocarbon is,
List the sources of hydrocarbon,
Identify the combustion products of organic carbon compounds
Activity 1 Fill in the blanks with the correct answer. 1 Carbon compounds are compounds that contain …………. as one of their constituent elements. 2 There are two groups of carbon compounds; ………………….. compounds and ………………..
compounds. 3 Carbon compounds that can be obtained from non-living things are classified as
………………..compounds. 4 Hydrocarbons are the simplest of all organic compounds. Hydrocarbon contains only two
elements, ……………………… and ………………………. 5 Organic compounds that contain carbon, hydrogen together with a few other elements such as
oxygen, nitrogen, phosphorus or halogens are called …………………………… 6 Hydrocarbons can be classified into two , ……………………….. and unsaturated hydrocarbons. 7. Hydrocarbons that contain only carbon-carbon single bond is called ……………………. 8 Hydrocarbons that contain at least one carbon-carbon double bond or carbon-carbon triple bond
is called …………… 9. Natural sources of hydrocarbons are ……………………, coal and natural gas. 10 Organic compounds burn in excess of oxygen gas to produce …………………….. and …………………….
b. Explain why on going down the alkane series, the melting and boiling point increase?
On going down the alkanes series, the ……………………………….. increases caused by the
increase in molecular size.
When the molecular size increases, the melting and boiling point ……………... This is
because the larger the molecular size, the stronger the ……………………….. forces of
attraction between the molecules. Thus more energy is needed to …………………. the
forces of attraction during melting or boiling.
c. Explain why alkanes are non-conductors of electricity.
Alkanes are covalent compounds made up of ………………………….
They don’t have ……… ..moving ions. Hence alkanes are non-conductors of electricity.
d Ethane and propene burn in excess of oxygen gas. Balance the chemical equation of the combustion of these hydrocarbons. (i) C2H6 (g) + O2 (g) CO2 (g) + H2O (l) (ii) C3H8 (g) + O2 (g) CO2 (g) + 4H2O (l) Activity 3 Complete the sentences with the correct word. 1 Carbon is placed in Group ……………..
2 It has ……………. electrons in its outer most shell.
3 An atom of carbon contributes ……………….. electrons to share with other atom of elements to
obtain the stable electron arrangement of inert gas elements.
4 Atoms in alkanes are bonded with ……………………… bond.
5 The first member in this group is the simplest compound called ……………….
E ALCOHOLS Learning outcomes You should be able to:
• state the general formula of alcohols, • identify the functional group of alcohols, • list the names and molecular formulae for the first four alcohols, • draw structural formulae for isomers of propanol (C3H7OH) and butanol (C4H9OH), • name isomers of propanol and butanol using IUPAC nomenclature, • describe the industrial production of ethanol. • ` describe the preparation of ethanol in the laboratory, • state the physical properties of ethanol, • predict the chemical properties for other members of alcohols, • explain with examples the uses of alcohol in everyday life, • explain the effects of the misuse and abuse of alcohols.
Activity 10 (a) Fill in the blanks by choosing the suitable answer from the text box below
i) Alcohol is one of the Homologue Series that has functional group of ……………..
ii) The general formula for alcohol is ……………………………….
iii) The melting point of alcohol is ……………….. than alkane and alkene due to the
presence of ……………………………….
iv) This is because the functional group forms hydrogen bonding that is …………..
than the bonds between molecules of alcohol.
v) Methanol, ethanol dan propanol dissolve in water. The solubility of other alcohols
decreases as the………………………… increases.
vi) Naming the alcohol compound is likely to ………….. C1 is numbered from the carbon that
nearest to the functional group..
vii) Alcohols are used as fuels, ………………., in medicine, in making ………………….
Activity 11 (a) Summarize the physical properties of ethanol in the table below
Physical properties Description
Physical state at room temperature
Smell and colour
Solubility in water
Volatility
Boiling point
(b) Ethanol can be prepared in two ways, Fermentation and Hydration. In fermentation process, (i) What is the function of yeast? ………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
………………………………………………………………………………………
(ii) Write the chemical equation to show the fermentation process. …………………………………………………………………………… (iii) State the temperature, catalyst and other condition needed for fermentation process.
…………………………………………………………………………………….
……………………………………………………………………………………..
(iv) State the disadvantages of this process.
……………………………………………………………………………………..
……………………………………………………………………………………..
……………………………………………………………………………………………..
(c) Hydration process involves hydration of ethene. Ethene is obtained from the cracking of petroleum fractions.
(i) Write the chemical equation for hydration process.
…………………………………………………………………………………..
(ii) State the temperature, pressure and catalyst needed for hydration process.
F CARBOXYLIC ACIDS Learning outcomes You should be able to :
state the general formula of carboxylic acids, identify the functional group of carboxylic acids, list the names and molecular formulae of the first four members of carboxylic acid, draw structural formulae of the first four members of carboxylic acid and name them using the IUPAC nomenclature, describe the preparation of ethanoic acid in the laboratory, state the physical properties of carboxylic acids, state the chemical reactions of ethanoic acids with other chemicals, predict the chemical properties for other members of carboxylic acid, explain with example the uses of carboxylic acids in everyday life
Activity 13 (a) Complete the diagram below.
Functional group :
CARBOXYLIC
ACIDS
Uses : a ……………………………… b ……………………………… c ……………………………… d ……………………………..
Ethanoic acid normally prepared by ………………… of an alcohol
b) Draw the set up of apparatus to prepare ethanoic acid .in laboratory Write the chemical reaction that involve. c) Write the observation of every test for ethanoic acid below.
Test Observation Inference
1 a. Ethanoic acid + metal carbonate
b. Gas released + lime water
2 a. Ethanoic acid + magnesium
b. Gas given off + lighted splinter
3 Ethanoic acid + copper (II)oxide
4 Glacial ethanoic acid + ethanol + concentrated sulphuric acid + heat Then the boiling contents are poured into a beaker half filled with water.
Activity 19 a) Complete the flow chart below to show the Extraction Process of Palm Oil. b) State 5 benefits of palm oil compared to other vegetable oils i) ………………………………………………………………….
ii) ……………………………………………………………………
iii) …………………………………………………………………..
iv) ………………………………………………………………….
v) ………………………………………………………………….
I NATURAL RUBBER
Learning outcomes: You should be able to :
List examples of natural polymers and their monomers,
Draw the structural formula of natural rubber,
State the properties of natural rubber,
State the uses of natural rubber
Describe the coagulation process of latex
Describe the method used to prevent latex from coagulating,
Describe the vulcanization of rubber,
Describe how the presence of sulphur atoms changes the properties of vulcanised rubber,
Compare and contrast the properties of vulcanised and unvulcanised natural rubber.
Oil palm fruit bunches
Stripping
Pressing
The fresh fruit bunches are sterilized ia large pressure vessels at 140o C for 60-90 min. The heat from the steam kills fungus and bacteria
Breaking down the oil-bearing cells. Crush the palm oil fruits
The mixture is filtered to remove solid or coarse fibre and allow to settle in an a large clarification tank. The oil is skimmed off and dried in a vacuum drier.
1 Base on the diagram above, (a) Name the product formed in step I.
………………………………………………………………………………………
(b) (i) State the reagents needed for step II.
…………………………………………………………………………
(ii) Write the chemical equation for the reaction in step II.
…………………………………………………………………………
(c) (i) Name the type of reaction occurring in step III.
………………………………………………………………………….
(ii) A catalyst is needed for the reaction in step III. Name the catalyst.
…………………………………………………………………………
(d) (i) Describe briefly how to carry out the reaction in step IV.
………………………………………………………………………….
(ii) What do you expect to observe when the reaction in step IV is carried out?
……………………………………………………………………………………
(e) Draw the possible structural formulae of C3H7OH formed in step V.
(f) (i) Name the type of reaction occurring in step VI.
………………………………………………………….
(ii) Give one use for ( C3H6)n formed in step VI.
………………………………………………………….
(g) Compare and explain the sootiness of C3H6 and C3H8 when each of these hydrocarbons is burnt in excess air. [Relative atomic mass: H = 1; C = 12) [4]
2 Diagram below shows the molecular formulae of 4 carbon compounds.
(a) Write the general formula of the homologous series of compound B.
……..……………………………………………………………………………………… (b) State the functional group of compound A and compound D
Compound A : ………………………………………………………………………….. Compound D : …………………………………………………………………………..
(c) Compound B shows isomerism. Draw the structural formula of all isomers of compound B.
(d) Compound D and compound C react in the presence of the concentrated sulphuric acid.
(i) Name the product formed from the reaction.
……………………………………………………….…………………………… (ii) State one special characteristic of the product formed.
……………………………………………………….……………………………
(e) Compound A burns in excess oxygen to produce carbon dioxide and water.
(i) Write a balanced chemical equation for the reaction. .................................................................................................................
(ii) 11.2 g of compound A burns in excess oxygen, calculate number of carbon
dioxide molecules formed. [Relative atomic mass C = 12, O = 16 and Avogadro number = 6.02 x 1023]
CHAPTER 3 : OXIDATION AND REDUCTION A. REDOX REACTIONS Learning Outcomes: You should be able to,
state what oxidation is
state what reduction is
explain what redox reaction is
state what oxidising agent is
state what reducing agent is
calculate the oxidation number of an element in a compound.
relate the oxidation number of an element to the name of its compound using the IUPAC nomenclature.
explain with examples oxidation and reduction processes in terms of electron transfer
explain with examples oxidising and reducing agents in redox reactions.
write oxidation and reduction half-equations and ionic equations.
Activity 1 1) The tables below describe the meaning of oxidation and reduction in terms of (a) loss or gain of oxygen (b) loss or gain of hydrogen (c) transfer of electrons (d) changes in oxidation number
Study each table below carefully and fill in the blanks. (a) Loss or gain of oxygen
Loss or gain of oxygen
Oxidation Reduction
The process of gaining oxygen The process of losing oxygen
Example : Mg + PbO MgO + Pb In the above redox reaction,
Mg gains oxygen to form MgO. This process is called. ……….………………………….
PbO loses oxygen to form Pb. This process is called ……….…………………………....
Mg is a reducing agent because it ………………….. … lead(II) oxide to …………………….
PbO is an oxidizing agent because it ………………… magnesium to………………………..
(b)Loss or gain of hydrogen
Loss or gain of hydrogen
Oxidation Reduction
The process of losing hydrogen The process of gaining hydrogen
Example : H2S + Cl2 2HCl + S
In the above redox reaction
H2S loses hydrogen to form S. The process is called …….. ………………………...
Cl2 gains hydrogen to form HCl. This process is called …….. ……………………….
H2S is a reducing agent because it ………………to …………………… ……..………….
Cl2 is an oxidizing agent because it ……………………to……………………………..
(c) Transfer of electrons
Transfer of electrons
Oxidation Reduction
The process of losing electrons The process of gaining oxygen
Example : Redox reaction: 2Na + Cl2 2NaCl Half-equations: Na Na+ + e // Cl2 + 2e 2Cl– In the half-equations above,
Na atom loses electron to form Na+. This process is called …………………………
Cl2 molecule gains electrons to form 2Cl–. This process is called …………………..
Na is a reducing agent because it …………………… to ………………………… ……..
Cl2 is an oxidizing agent because it …………………..to ………………………… …….
(d) Changes in oxidation number
Changes in oxidation number
Oxidation Reduction
The increase in oxidation number The decrease in oxidation number
Example : Chemical equation: 2Na + Cl2 2NaCl
Changes in oxidation number Na : 0 +1 // Cl : 0 –1 Given above are the changes in oxidation number of Na and Cl, state which element is oxidized or reduced and which element is the oxidizing or reducing agent.
Na is ............................. to Na+ : Na is the………………………………..… agent
Cl2 is …………………….to Cl– : Cl2 is the …………………………………. agent
Activity 3 (a) Fill in the blanks with suitable words. (i) The substance that causes oxidation is called the ………………………….………….. agent
(ii) The substance that causes reduction is called the ……………...…………………….. agent.
(b) State the oxidizing and reducing agents in each of the chemical reactions given below. (i) 2Zn + O2 2ZnO.
Oxidising agent: ……………………………... Reducing agent: …….………………………….. (ii) 2Mg + CO2 2MgO + C Oxidising agent: .…………………….……… Reducing agent: ……..…………………………….. Activity 4 Oxidation numbers of elements can be calculated based on the ‘rules in assigning oxidation numbers’ as stated in the chemistry text book on page 107. Two examples are given below. Examples: a) Determine the oxidation number for the underlined elements
(i) H3PO4 (1×3) + P + (-2×4) = 0 3 + P + (-8) = 0
P = 8 – 3 = +5 the oxidation number for phosphorus is +5
(ii) N2H4 2N + (1×4) = 0 2N + 4 = 0
N = – 4/2 = –2 the oxidation number for nitrogen is –2
Answer the following questions. 1. Determine the oxidation number for the underlined elements.
4 Determine the oxidation number for the underlined elements in the table below and name the compound using the IUPAC nomenclature.
Formula of compound Oxidation number Name of compound
CuSO4 Cu2O CrCl3
Cr2O72–
NO3–
NO2–
NH4+
MnO2 Activity 5 For each of the chemical reactions below, (a) write the oxidation and reduction half-equations, (b) identify the following: (i) Substance that undergoes oxidation (iii) Oxidising agent (ii) Substance that undergoes reduction (iv) Reducing agent Example: Zn + 2Ag+ Zn2+ + 2Ag Based the ionic equation given, it is known that the oxidation number of Zn increases from 0 to +2. Hence zinc undergoes oxidation to form Zn2+ Answer: Oxidation half-equation: Zn Zn2+ + 2e- Reduction half-equation: 2Ag+ + 2e- 2Ag Substance undergoes oxidation: Zinc (Zn) Substance undergoes reduction: Silver ion (Ag+) Oxidising agent : Silver ion (Ag+) Reducing agent : Zinc (Zn) Based on the chemical equation given, complete the flow charts below. a)
Activity 6(a) Writing ionic equation from given oxidation and reduction half-equations: Example: Given: Oxidation half-equation: Mg Mg2+ + 2e Reduction half-equation: Ag+ + e Ag [In order to write an ionic equation from the two given half-equations, the electrons that were transferred from Mg to the Ag must be equal. Hence two Ag+ will receive two electrons from an atom of Mg.]
Mg Mg2+ + 2e 2Ag+ + 2e 2Ag
Mg + 2Ag+ Mg + 2Ag Answer: Ionic equation: Mg + 2Ag+ Mg + 2Ag Based on the given oxidation and reduction half-equations, write the ionic equation for the reaction (a) Oxidation half-equation: Mg Mg2+ + 2e Reduction half-equation: Cu2+ + 2e Cu Ionic equation: ………………………………………………………………………………… (b) Oxidation half-equation: Al Al3+ + 3e Reduction half-equation: Ag+ + e Ag Ionic equation: ………………………………………………………………………………… (c) Oxidation half-equation: Fe2+ Fe3+ + e Reduction half-equation: Br2 + 2e 2Br–
Ionic equation: ………………………………………………………………………………… (d) Oxidation half-equation: 2I– I2 + 2e Reduction half-equation: Cl2 + 2e 2Cl–
Ionic equation: ………………………………………………………………………………… (e) Oxidation half-equation: Cl2 + 2e 2Cl–
Reduction half-equation: Fe2+ Fe3+ + e Ionic equation: ………………………………………………………………………………… (f) Oxidation half-equation: Fe Fe2+ + 2e Reduction half-equation: O2 + H2O + 4e 4OH–
Procedure: 1. 2.0 cm3 of ............................................. solution is added into a test tube.
2. A few drops of ...................... …….............. were added drop by drop into the test tube and mixture
is heated.
3. The ……………………………… is recorded.
4. Observation:
The colour of iron(II) sulphate solution changed from ....................... to ................... The bromine water changed from ....................... to ........................ . In order to detect presence of iron(III) ion in the solution, add .......................... ........................................ ………............... in excess. ..................................(colour) precipitate of iron(III) hydroxide is formed.
5. Concept: a) Iron(II) ion is ……………… to iron(II) ion by ……………………………. At the same time
1. A ..…………. (more/ less) electropositive element is oxidized more …………………. (easily / harder )
and acts as a ……………………….. (stronger / weaker) reducing agent.
2. An element that is located higher in the electrochemical series can displace other elements that are
positioned (i)……………………….. in the electrochemical series from its salt solution.
Example: Displacement copper from copper(II) sulphate solution. Ionic equation: Zn + CuSO4 ZnSO4 + Cu Half-equation: Zn Zn2+ + 2e [ Oxidation ] Half-equation: Cu2+ + 2e Cu [ Reduction ] Zinc, Zn is (ii) ……………. electropositive than copper, Cu. Thus Zn atom releases (iii) ……………. electron to form ion Zn2+. The electrons are transferred from (iv)…………… ……….….. to (v)…………………………….. The copper(II) ion, Cu2+ receives the two electrons from zinc to form copper atom, Cu. Zn atom acts as a (vi) …………………… …………… and Cu2+ ion acts as a (vii) ………………………………… …………………
Activity 8 (a) Halogen in aqueous and 1,1,1-trichloroethane Complete the table below by stating the colur of halogen in aqueous solution and in 1,1,1-trichloroethane
Halogen Colour of halogen
In aqueous solution In 1,1,1,-trichloroethane
Chlorine
Bromine
Iodine
Displacement of halogens from their halide solutions by other halogens.
Fill in the blanks by choosing the most appropriate word from the list displayed above. 1) Halogens are located in Group ………….. of the Periodic Table
2) Halogen elements tend to ………………… electrons to achieve a stable octet electron arrangement. 3) Halogens are reduced to …………… ions 4) The electronegativity of halogens or their tendency to accept electrons ………………….. when going
down Group 17. 5) Thus, the strength of halogens acting as ………………… ….……….. decreases when going down
the group 17. 6) In displacement reaction of halogen, a ……….. electronegative halogen will displaces a …………… electronegative halogen from its halide solution. Activity 9 Transfer of electrons at a distance A. The diagram shows the set up of apparatus for the redox reaction involving bromine water and
potassium iodide solution.
The following statement describe the redox reaction between bromine and potassium iodide solution. Fill the blanks with the appropriate word(s). 1. Electrons flow from …………….. to ….…………through the wire. 2. The colour of potassium iodide solution changes from ………………………to ………………………. 3. The colour of bromine water changes from ………………… to ………………… …………………….... 4. Oxidation half-equation: …………………………………………………………………………………..
5. Overall Ionic Equation : …………………………………………………………………………………….. 6. Oxidising agent: ……………………………… 7. Reducing agent: ………………………… 7. To confirm that the brown solution formed is iodine solution, a chemical test can be carry out.
Some ....................... ......................... is added into a test tube containing the brown solution. A dark blue colouration is obtained if iodine is present. Method 2 2 cm3 of ........................................... is added into a test tube containing the brown soltion. The
test tube is then stopperred and its mixture .................. If the lower layer [1,1,1-trichloroethane
layer] is ............................. in colour, then it is confirmed iodine is present.
B The diagram below shows the set up of apparatus of redox reaction between acidified potassium
manganate(VII) and potassium iodide soultion.
Below are some of the facts about the redox reaction between acidified potassium manganate(VII)
and potassium iodide soultion. Answer the following question The half-equation for the reaction that occurs around the carbon rod on the left is as follow
MnO4- + 8H + + 5e Mn 2+ + 4H2O
a) State the change in oxidation number of manganese.
…………………………………………………………………………..
b) A brown solution was observed forming around the carbon rod on the right. Name the brown
solution formed. ..……………………………………………………………………………….. c) Write a half-equation for the formation of the brown solution.
………………………..…………………………………………………………………………..
d) Write the ionic equation for the reaction between acidified potassium manganate(VII) and iodide ion.
2. Mechanism of rusting of iron in the present of water and oxygen involves some chemical
reactions. Figure below shows an unlabeled diagram of a water droplet on the surface of iron.
Write the chemical equations or half equations for the processes below.
a) The formation of iron(II) ions from the metal: When iron contacts with water, the iron surface oxidizes to form iron(II) ions. Oxidation half-equation: ……………………………………………………………………….
b) The formation of hydroxide ions:
Electrons released by iron then flow to the edges of the water droplets, where there is a high concentration of dissolved oxygen. At the cathode area, water and oxygen molecules receive electrons and are reduced to form hydroxide ions. Reduction half-equation: ……………………………………………………………………………..
c) Formation of green precipitate. Fe2+ readily combines with OH- to form insoluble solid Fe(OH)2 Chemical equation: …………………………………………………………………………………..
d) Using chemical equations in (a), (b) and (c), the reaction between iron, water and oxygen to form iron(II) hydroxide can be summarized into a overall chemical equation. Chemicall equation: ……………………………………………………………………………………..
e) With excess oxygen, the rust is formed: The Fe2+ ions are further oxidized to form Fe3+ ions, which reacts with OH- ions to form the hydrated iron (III) oxide, Fe2O3. xH2O, known as ‘rust’.
Chemical equation: ……………………………………………………………………….
f) Complete the diagram above by filling the blanks in the spaces provided.
(c) Which test tube shows the highest rate of rusting of iron? Explain your answer. ..................................................................................................................................................... ......................................................................................................................................................
(d) Arrange the metals Fe, P and Q in decreasing order of electrochemical series.
(f) State the ion that causes the solution in test tube C to turn pink. ...................................................................................................................................................
C. THE REACTIVITY SERIES OF METALS WITH OXYGEN AND ITS APPLICATION Learning Outcomes : You should be able to,
compare the differences in the vigour of the reactions of some metals with oxygen.
deduce the reactivity series of metals.
determine the position of carbon and hydrogen in the reactivity series of metals.
state what the reactivity series of metals are.
describe the extraction of iron and tin from their ores.
explain the use of carbon as the main reducing agent in metal extraction.
use the reactivity series of metals to predict possible reactions involving metals
Activity 13 1. Figure below shows the set-up of apparatus for an experiment to determine the order of
metals in the reactivity series. Solid potassium manganate (VII) is heated to release oxygen gas to react with hot metal powder.
The experiment is carried out using metal powders of copper, zinc, magnesium and lead . The observation of the experiments on the metal powders of copper, zinc, magnesium and lead in the experiments are shown in table below.
(iv) Lead + oxygen ……………………………………………………………………………………………
2) According to the chemical equation below, carbon reacts with oxygen to produce ……………
………………………….. gas.
C ( s ) + O2 (s ) → CO2 ( g )
3) Based on the reactivity series of metals with oxygen, carbon able to displace a …………… ……………….. metal from its metal oxide. Thus, by heating a mixture of metal
oxide and carbon , the reactivity of carbon can be determined.
0 Oxidation +4
C ( s ) + 2PbO (s ) → CO2 ( g ) + 2Pb(s) +2 Reduction 0
4) Carbon is ………………… to carbon dioxide and lead (II) oxide is reduced to lead. 5) Carbon acts as a (i)…………………………….. agent which displaces a metal from its oxide while the metal oxide is the (ii) …………………….agent.
6) Carbon is not able to displace a …………… ………………. metal from its metal oxide. Hence,
there is no displacement reaction when a mixture of magnesium oxide and carbon is heated.
7) Carbon is positioned in between (i) …………………………and (ii) …………….. in the reactivity
series.
8) Oxides of metals W,X, Y, Z are heated with equal amount of carbon powder in an experiment to compare their reactivity with carbon. The changes observed are recorded in the table below.
Mixture Observation
Carbon + oxide of W No change
Carbon + oxide of X Dim glow. Grey residue is formed
Carbon + oxide of Y No change
Carbon + oxide of Z Bright glow. Brown residue is formed
(a) Based on the observation , classify the metals in groups that are
(i) more reactive than carbon: ………………………………………………………………… (ii) less reactive than carbon: …………………………………………………………………
(b) Suggest a possible element for metals X and Z
X : …………………………………… Z : ………………………………………….
(c) The reactivity of W and Y can be compared by heating an equal amount of W powder with oxide of Y in a crucible using the same apparatus set-up.
(i) What is the expected observation if W is more reactive than Y? Explain your answer ……………………… ……………………………………………………………………… ………………………………………………………………………………………………… (ii) Suggest the possible elements for W and Y W : ………………………………… Y : ……………………………………………….. (iii) Write a balanced chemical equation for the reaction between W (charge of +2) and
oxide of Y (charge of +3). …………………….. …………………………………………………………………..
(iv) Identify the reducing agent and oxidising agent in the reaction between W and oxide
of Y. Reducing agent: ………………..……… Oxidising agent: ……………………………
9. Complete the reactivity series of metals with oxygen given below by writing the name of the missing elements in the spaces provided. Reactivity decreases
Potassium
Calcium
Aluminium
Iron
Tin
Mercury
Gold
10. The following shows part of the increasing order of reactivity series of metals with oxygen.
K Na Ca Mg Al Zn Fe Sn Pb Cu Hg Ag Au Insert the positions of carbon and hydrogen in the above series by using arrows to indicate its
position. 11. Predict what will be observed when, (a) hydrogen gas is heated with copper (II) oxide in tube. ……………………..…………………………………………………………………………............ …………………….…………………………………………………………………………………. (b) a piece of burning magnesium ribbon is dropped into a gas jar filled with carbon dioxide.
……..……………………………………………………………………..……………………………
…………………………………..…………………………………………………………………….
(c) carbon is heated with magnesium oxide. …………………………………………………………………………………………....................
12. Complete the following table by giving the main mineral in ore and the metal extracted from its ore.
Ore Main mineral in ore
Metal extracted Name Formula
(a) Bauxite
(b) Hematite
(c) Magnetite
(d) Cassiterite
D. ELECTROLYTIC AND CHEMICAL CELLS Learning Outcomes : You should be able to,
explain with examples the oxidation and reduction reactions at the electrodes of various chemical cells.
explain with examples the oxidation and reduction reactions at the electrodes of various electrolytic cells.
state the differences between electrolytic and chemical cells in terms of basic structure, energy conversion and the transfer of electrons at the electrodes .
compare and contrast electrolytic and chemical cells with reference to the oxidation and reduction process.
Activity 14 1) Below are listed the differences between electrolytic and chemical cells. Complete the statements by filling in the blanks with the correct words.
It requires a source of ……………………………………. The electrodes may be of the ………… material such as …………………
It does not require a source of ……………………………………
The electrodes must be of two …………………...... metals.
HEAT OF REACTION Activity 4: Match the chemical equation with the type of reaction below :
Chemical equation
Type of reaction
HNO3 + KOH KNO3 + H2O Precipitation
C2H5OH + 3O2 2CO2 + 3H2O Displacement
Mg + CuSO4 MgSO4 + Cu Neutralization
Pb(NO3)2 + 2KI PbI2 + 2KNO3 Combustion
HEAT OF REACTION The change in the amount of heat in a chemical reaction
Symbol : ΔH The
HEAT OF PRECIPITATION
HEAT OF DISPLACEMENT
HEAT OF NEUTRALIZATION
HEAT OF COMBUSTION
The heat change in a reaction can be calculated using the formula , H = mcӨ m = mass of solution, g c = specific heat capacity of the solution, J g-1 oC-1 Ө = temperature change , 0C Assumption : i) The solution is dilute, it has the same density as water , 1 g cm-3 ( 1 cm3 = 1 g ) ii) The solution has the same specific heat capacity as water, 4.2 J g-1 oC-1
Learning Outcomes You should be able to:
State what heat of reaction is,
State what heat of precipitation is,
Determine the heat of precipitation for a reaction,
Construct an energy level diagram for a precipitation reaction,
Solve numerical problems related to heat of precipitation
Activity 5 : (a) What is meant by heat of precipitation ? ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. (b) To determine the heat of precipitation of silver chloride, AgCl Procedure : 1. Measure 25 cm3 0.5 mol dm-3 silver nitrate solution and pour it into the polystyrene cup,
Example :
Calculate the amount of heat change when the temperature of 200 cm3 of water is raised from 280C to 400C, Q = mcӨ m = 200 g = 200 g x 4.2 J g-1 oC-1 x 12 0C c = 4.2 J g-1 oC-1 = 10080 J Ө = 40 - 28 = 12 0C = 10.08 kJ
Guidelines for the calculation of the heat of reaction Steps to follow: Step 1 - Calculate the heat change using the formula, H = mcӨ ( p Joule ) Step 2 - Write chemical equation or ionic equation for the reaction that occurs Step 3 - Calculate the number of moles of reactant that reacts using either the following formulae : Number of moles = mass = q mol or molar mass Number of moles = MV ( q mol) M : Molarity of the solution (Solution) V : volume of the solution in dm3 Step 4 - Link the number of moles of reactants ( step 3 ) with the heat change ( step 1 ) q mol of reactants react heat lost/gain is p J
∴ 1 mol of reactants react heat lost/gain is p J
q Heat of reaction , ΔH = +/- p kJ mol-1
1000 x q = +/- r kJ mol-1 Note : “ + “ is used for endothermic reaction and “-“ is used for exothermic reaction
2. Put the thermometer into the silver nitrate solution. Record the initial temperature, 3. Measure 25 cm3 0.5 mol dm-3 sodium chloride solution and record the initial temperature, 4. Pour the sodium chloride solution quickly into the silver nitrate solution in the polystyrene cup. 5. Stir the solution mixture with the thermometer and record the highest temperature achieved. Result : Initial temperature of silver nitrate solution = 28.5 0C Initial temperature of sodium chloride solution = 29.5 0C Highest temperature of the mixture = 32.0 0C Calculation
Step 1 : Calculate the heat change using the formula H = mcӨ
Temperature change, Ө = 32.0 0C - 29.0 0C = 3.0 0C Heat change , H = mcӨ m = ( 25 + 25 ) g = 50 g c = 4.2 J g-1 oC-1
Ө = 3.0 0C H =(1) ……….........J
Step 2: Write balanced chemical equation or ionic equation for the reaction that occurs
Chemical equation : AgNO3 (aq) + NaCl(aq) AgCl (s) + NaNO3 (aq) Precipitate
Ionic equation : (2)………………………………………………………. Deduce the mole ratio from the ionic equation : (3)…………mol silver ion, Ag+ react with (4) ……… mol of chloride ion, Cl- to produce (5)……………. mol of silver chloride , AgCl.
Step 3 : Calculate the number of moles of reactant that reacts, Use the formula : n = MV ( V in dm
3 )
Number of moles of silver ion = the number of moles of silver nitrate = (6) …………………….. mol Number of moles of chloride ion = the number of moles of sodium chloride = (7)…………………….. mol Number of moles of silver chloride formed = (8) ………………….. mol
Step 4 Calculate the heat of precipitation of silver chloride, ΔH Step 5 Energy level diagram
When (9) ….. mol of silver chloride formed, heat released is (10) .…….. When 1 mol of silver chloride formed, heat released is (11)...................... Heat of precipitation of silver chloride, ΔH = (12) - ……………kJ mol – 1 Draw the energy level diagram for the reaction that occurs in this experiment (13)
(c) (d)
Calculate the heat change when 200 cm3 of 0.5 mol dm-3 calcium chloride, CaCl2 solution is added to 200 cm3 of 0.5 mol dm-3 sodium carbonate, Na2CO3 solution if the heat of precipitation of calcium carbonate, CaCO3 is +12.6 kJ mol-1 [ Specific heat capacity of solution : 4.2 J g-1 0C-1 . Density of solution : 1 g cm-3 ] The thermochemical equation for the precipitation of silver chloride is as follows : Ag+ (aq) + Cl- (aq) AgCl ΔH = –65.5 kJ mol-1
Calculate the temperature change when 100 cm3 of 0.5 mol dm-3 silver nitrate, AgNO3 ,
solution is added to 100 cm3 of 0.5 mol dm-3 potassium chloride, KCl solution
C HEAT OF DISPLACEMENT Activity 6 (a) What is meant by the heat of displacement ? ………………………………………………………………………………………………………….. ………………………………………………………………………………………………………….. (b) To determine the heat of displacement of copper from a copper (ll) sulphate solution by zinc.
Procedure : 1. Measure 25 cm3 0.2 mol dm-3 copper(ll) sulphate solution and pour into a polystyrene cup. 2. Put the thermometer into the copper(ll) sulphate solution. Record the initial temperature, 3. Add half a spatula of zinc powder (in excess) quickly into copper(ll) sulphate solution. 5. Stir the mixture with the thermometer and record the highest temperature achieved. Result : Initial temperature of copper(II) sulphate solution = 30.0 0C Highest temperature of the mixture = 40.0 0C Calculation
Step 1 : Calculate the heat change using the formula H = mcӨ
Changes of temperature, Ө = 40.0 0C - 30.0 0C = 10.0 0C Heat change , H = mcӨ m = 25 g c = 4.2 J g-1 oC-1
Ө = 10.0 0C H = (1)…………………………….. J
Step 2: Write balanced chemical equation or ionic equation for the reaction that occurs
Chemical equation : Zn (s) + CuSO4(aq) Cu (s) + ZnSO4 (aq) copper displaced
Deduce the mole ratio from the equation : (2)……… mol copper metal, Cu is displaced from (3) …………….. mol of copper(ll) sulphate solution, CuSO4 by zinc
Step 3 : Calculate the number of moles of reactant that
Number of moles copper(ll) sulphate = (4)…………………….. mol Number of moles of copper = (5)…………………….. mol
zinc powder
25 cm3 0.2 mol dm
-3
copper(ll) sulphate solution
Learning Outcomes, You should be able to:
State what heat of displacement is,
Determine the heat of displacement,
Construct an energy level diagram for a displacement reaction,
Solve numerical problems related to heat of displacement,
Step 4 Calculate the heat of displacement of copper, ΔH Step 5 Energy level diagram
When (6) ….. mol of copper is displaced, the heat released is (7) .……..
∴ When 1 mol of copper is displaced, the heat released is (8).................
Heat of reaction , ΔH = (9) ……………… kJ mol – 1
Draw the energy level diagram for the reaction that occurs in this experiment (10)
(c) Figure shows an experiment carried out to determine the heat of displacement of silver from silver nitrate by copper metal. Based on figure above, calculate the heat of displacement for the reaction. (d)
In an experiment, excess magnesium powder is added to 50 cm3 of 0.25 mol dm-3
iron(ll) sulphate solution at 29.0 0C. The thermochemical equation is shown below,
Mg(s) + Fe2+ (aq) Mg2+ (aq) + Fe (s) ΔH = -80.6 kJ mol - 1 What is the highest temperature reached in this experiment ?
Activity 7 (a) What is meant by the heat of neutralization ………………………………………………………………………………………………………….. …………………………………………………………………………………………………………… (b) To determine the heat of neutralisation between a strong acid ( hydrochloric acid ) and a strong alkali ( sodium hydroxide ) Procedure : 1. Measure 50 cm3 2.0 mol dm-3 sodium hydroxide solution and pour it into the polystyrene cup,
2. Put the thermometer into the sodium hydroxide solution. Record the initial temperature, 3. Measure 50 cm3 2.0 mol dm-3 hydrochloric acid solution and record the initial temperature, 4. Pour the hydrochloric acid solution quickly into the sodium hydroxide solution in the polystyrene cup. 5. Stir the mixture with the thermometer and record the highest temperature achieved. Result : Initial temperature of sodium hydroxide solution = 29.0 0C Initial temperature of hydrochloric acid solution = 29.0 0C Highest temperature of the mixture = 42.0 0C Calculation
Step 1 : Calculate the heat change using the formula H = mcӨ
Changes of temperature, Ө = 42.0 0C - 29.0 0C = (1) ……………….0C Heat change , H = mcӨ m = ( 50 + 50 ) g = 100 g c = 4.2 J g-1 oC-1
Ө = (2) ……………….0C H = (3)…………………………….. J
Step 2: Write balanced chemical equation
Chemical equation (4) ………………………………………………………….
Ionic equation (5) ……………………………………………………….
Learning Outcomes : You should be able to: State what heat of neutralization is, Determine the heat of neutralization, Construct energy level diagrams for various types of neutralization reactions, Compare the heat of neutralization for the reactions between a strong acid and a strong alkali with the heat of neutralization for a reaction between a weak acid and a weak alkali, Explain the difference of the heat of neutralization for a strong acid and a strong alkali with heat of neutralization for a reaction involving a weak acid and/or a weak alkali. solve numerical problems related to heat of neutralization,
Deduce the mole ratio from the ionic equation : (6)……mol hydrogen ion, H+ react with (7)……mol of hydroxide ion, OH- to produce (8)……………. mol of water , H2O
Step 3 : Calculate the number of moles of reactant that reacts, Use , n = MV
( V in dm3 )
Number of moles of H+ = the number of moles of hydrochloric acid = (9)…………………….. mol Number of moles of OH- = the number of moles of sodium hydroxide = (10)…………………….. mol Number of moles of water formed = (11) ………………….. mol
Step 4 Calculate the heat of neutralisation of hydrochloric acid and sodium hydroxide, ΔH Step 5 : Energy level diagram
When (12) ….. mol of water formed, heat released is (13) .……..
∴ When 1 mol of water formed, heat released is (14) .................
Heat of neutralisation , ΔH = (15) ……………… kJ mol - 1 Draw the energy level diagram for the reaction that occurs in this experiment (16)
(c)
The thermochemical equation for the reaction between ethanoic acid and sodium hydroxide is given below, CH3COOH (aq) + NaOH (aq) NaCH3COO (aq) + H2O (l) ΔH = -55 kJ mol - 1 Calculate the heat given out when 200 cm3 of ethanoic acid 0.5 mol dm-3 is added to 200 cm3 of sodium hydroxide 0.5 mol dm-3
(d) The energy level diagram of a neutralization reaction is shown in figure below Energy
H2SO4 + 2NaOH
ΔH = - 114 kJ Na2SO4 + 2H2O
When 100 cm3 of 1.0 mol dm-3 sulphuric acid is added to 100 cm3 of 1.0 mol dm-3 sodium hydroxide solution. What is the change in temperature?
E : HEAT OF COMBUSTION Activity 8 : (a) What is meant by the heat of combustion ………………………………………………………………………………………………………. (b) To determine the heat of combustion of ethanol
Learning Outcomes You should be able to :
state what heat of combustion is,
determine heat of combustion for a reaction,
construct an energy level diagram for a combustion reaction,
compare the heats of combustion of various alcohols,
state what fuel value is,
describe the difference between heats of combustion of various alcohols,
describe the applications of fuel value,
compare and contrast fuel values for various fuels,
solve numerical problems related to heat of combustion.
Experiment to determine the heat of combustion. Procedure : 1. Measure 200 cm3 of water and pour it into a copper can. Record the initial temperature of the water and place the copper can on a tripod stand. 2. Fill a lamp with ethanol and weigh it. Record the mass of the lamp together with its content. 3. Light up the wick of the lamp immediately. Stir the water continuously until the temperature of the water increases by about 30 0C. 5. Put off the flame and record the highest temperature reached by the water 6. Weigh again the lamp and record the mass of the lamp. Result : Mass of lamp and ethanol before burning = 190.55 g Mass of lamp and ethanol after burning = 189.80 g Initial temperature of water = 29.00C Highest temperature of water = 59.00C Calculation
Step 1 : Calculate the heat change/heat absorbed by the water using the formula, H = mcӨ
Changes of temperature, Ө = 59.00C - 29.00C = 30.0 0C Mass of water, m = 200 g Heat change/ heat absorbed by water , H = mcӨ c = 4.2 J g-1 oC-1
Ө = 30.0 0C H = (1)…………………………….. J
Step 2: Write a balanced chemical equation for the combustion of ethanol
C2H5OH + (2)……………= (3)……………+ (4) ……………………….
Step 3 : Calculate the number of moles of ethanol that is used in the experiment, [ Relative atomic mass : H, 1 : C,12; O,16 ]
Mass of ethanol burnt/used = (5) ………………. g Number of moles of ethanol burnt = (6) __________ molar mass of ethanol = …………………….. mol
Step 4 Calculate the heat of combustion of ethanol, ΔH
When(7) ….. mol of ethanol is burnt in oxygen heat released is(8) .……
∴ When 1 mol of ethanol is burnt in oxygen, heat released is (9) ..........
Heat of combustion of ethanol , ΔH = (10) ……………… kJ mol - 1
Draw an energy level diagram for the combustion of ethanol in this experiment (11)
(c) The following results are obtained by a student in an experiment to determine the heat of combustion of alcohols. Complete the table and calculate the heat of combustion of methanol, propanol and butanol based on the data given in the table below . [ Relative atomic mass : H,1 ; C,12 ; O,16 . Specific heat capacity of water , 4.2 J g-1 0C-1 ]
Alcohol Methanol
Propanol
Butanol
Volume of water/cm3 200
200 200
Initial temperature of water / 0C
28.0 28.0 28.0
Final temperature of water / 0C
60.0 58.0 59.0
Mass of alcohol burnt/g
1.184
0.750
0.719
Changes in temperature / 0C
(1) (2) (3)
Molecular formula
(4) (5) (6)
Number of carbon atoms
(7) (8) (9)
Molar mass
(10) (11) (12)
Number of moles of alcohol burnt
(13) (14) (15)
Heat change/ absorbed by the
water / J
(16) (17) (18)
Heat of combustion of alcohol /
kJ mol-1
(19) (20) (21)
(i) State the relationship between the number of carbon atoms in an alcohol and the heat of combustion, ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………….
(ii) Predict the heat of combustion for pentanol ………………………………………………………………………………………………………………. (d) (e)
When 1 mole of butanol, C4H9OH is burnt in excess of oxygen, 2600 kJ of heat is produced. Calculate the mass of butanol needed to burn completely in oxygen in order to raise the temperature of 500 cm3 of water by 300C ( Relative atomic mass : H , 1 ; C , 12 ; O , 16, Specific heat capacity of water , 4.2 J g-1 0C-1) The heat of combustion of propanol, C3H7OH is -2016 kJ mol -1 What is its fuel value ? Solution : (i) Calculate the molar mass of propanol, C3H7OH. (ii) Calculate the fuel value of propanol, C3H7OH.
The fuel value of a fuel is the amount of heat energy given out when one gram of the fuel is completely burnt in excess of oxygen.
Fuel value ( kJ g-1 ) = heat of combustion of alcohol ( kJ mol-1 ) molar mass
1. Soap are……………….. or …………………… salts of long-chain fatty acids. 2. General formula of a soap is………………….. or ………………….. 3. Examples of soap are ………………………. and …………………..
4. Soap cannot be used in hard water which contains the salt of………………….. and
…………………
5. The process of the production soap is known as …………………………. 6. The two materials used to prepare soap are ………………….. and …………………..
7. When soap dissolved in water, it reduces the ……………………… of water.
Activity 2 : Preparation of soap
A. 50 cm3 of distilled water and two spatulas of table salts (sodium chloride) are added.
B. 25 cm3 of concentrated sodium hydroxide solution is added in the same beaker
C. The mixture is boiled and stirred for a few minutes
D. The mixture is boiled slowly while being stirred with a glass rod for 15 minutes
2. Name another substance that can be used to replace sodium hydroxide,NaOH solution in the
preparation of soap.
…………………………………………………………………………………………… 3. Why was sodium choride, NaCl used in this activity?
…………………………………………………………………………………………… 4. Write a word equation for the reaction between palm oil and sodium hydroxide.
…………………………………………………………………………………………..
E. The observations are recorded in the table provided
F. The mixture in the beaker is left to cool down and the resulting white solid is filtered
G. The following tests are carried out on the white solid: a) Touched using a finger b) Some of the white solid is shaken together with water in a test tube. c) Tested with a red litmus paper.
H. 5 cm3 of palm oil is poured into a beaker
I. The white solid that is produced is washed with a little water and dried with the filter paper
Activity 5 Complete tables with the correct answers. (Refer to page 182 – 186 from your text book)
DIFFERENCES BETWEEN SOAP AND DETERGENT
SOAP DETERGENT
DEFINITION ………… or potassium salts of long-chain fatty acids.
Sodium salt of..……… acid
EXAMPLES Sodium laurate ,CH3(CH2)10COONa,
…………. palmitate,
CH3(CH2)14COONa+
……………….,CH3(CH2)16COOK+
Potassium oleate, CH3(CH2)7CH=CH(CH2)7COOK+
Sodium alkyl sulphate
Sodium alkyl benzene sulphonate.
The ……………….. part of the soap/detergent is attracted to the water molecules.
The ………………… action helps to lift off the grease from the cloth.
The grease is broken into ……………… during scrubbing. These droplets remain suspended and separated as an ……………….. due to the repulsion between the negative charges on the surface
To enhance the cleaning efficiency of detergent by softening the water
Carboxymethylcellulose (CMC)
To prevent the dirt particles removed from redepositing onto cleaned fabrics.
Filler
Sodium sulphate, sodium silicate.
Foam control agent
-
To add fragrance to both the detergent and fabrics.
Activity 7 : Cleansing Action Of Soap And Detergent (Refer to page 184 and 185 from your text book to answer the following questions) 1 The statement below is about soap and detergent.
The cleaning action of a detergent is more effective than soap in hard water.
You have two socks stained with oil. Describe briefly the experimental procedure, observations and conclusions to prove the above statement, by using substances such as soap, detergent and hard water. Procedure of the experiment: ……………………………………………………………………………………….. ……………………………………………………………………………………….. ……………………………………………………………………………………….. ………………………………………………………………………………………. ……………………………………………………………………………………….
2 The following equation shows a reaction in the preparation of soap in a laboratory. Palm oil + Concentrated sodium hydroxide sodium palmitate(soap) + glycerol a) What is the name of this reaction?
……………………………………………………………………………… b) What is the homologous series of palm oil? ……………………………………………………………………………..
c) Complete the anion part of the soap particle in the space provided
3 A pupil wants to prepare potassium palmitate soap.
What alkali should he use? ……………………………………………………………………………………………….
4 Figure 2.1 shows part of the washing action of detergent particle on grease stained cloth.
i) State the part of a detergent particle that is soluble in grease.
……………………………………………………………………………………..
ii) Based on figure 2.1 explain the washing action of detergent particles on greasy stains.
B .FOOD ADDITIVES Learning Outcomes: You should be able to
State the types if food additives and their examples.
State the functions of each type of food additives.
Justify the use of food additives.
Describe the effects of food additives on health and the environment.
ACTIVITY 8 1. A food additive is a natural or synthetic substance which is added to food
to_________________ or ____________________its appearance, ________________ or ____________________ 2. Complete the chart. 3. Complete the following table.
Type of food additive.
State the function Give two examples
To slow down the growth of microorganisms so that food can be kept for longer periods of time.
Salt, vinegar, benzoic acid.
To prevent oxidation that causes rancid fats and brown fruits
Vitamins C and E
To improve the taste of food and restore taste loss due to processing.
To prevent emulsion from separating out
To thicken food
To add or restore the color in food to enhance Its visual appeal.
4. What are the advantages and disadvantages of using food additives?
ADVANTAGES DISADVANTAGES
5. Figure 5.6 shows a part of the label of a tin of baked beans. a) State the food additives present in the food.
b) To which type of food additives does each of the ingredients mentioned in (a) belong
Food additives present in baked beans in tomato sauce
Type of food additives
6. Sugar is used as food preservative as well as for sweetening. Patients with medical conditions such as diabetes mellitus or obesity must be wary of their intake of sugar.
a) i) Name one artificial sweetener that can replace sugar.
……………………………………………………………………………………… ii) Name one natural sweetener that can replace sugar.
………………………………………………………………………………………
b) Artificial food colorings are used in some processed foods. Suggest two reasons for using food coloring.
Activity 10 : Modern Medicines Complete the table below for classification of modern medicines and its function. (Please refer to page 198 – 201 from your text book)
Type of modern drugs Examples Uses
a) Analgesic
Aspirin
Paracetamol
Codeine
To relieve pain .……………………………… To treat headache and cough
b) ……………………..
Penicillin
Streptomycin
To cure bacterial diseases such as tuberculosis (TB) and pneumonia. …………………………………
6. Penicillin and streptomycin are the examples of antibiotics. a) What is the function of an antibiotic?
…………………………………………………………………………………… b) Why are penicillin and streptomycin given by injection and not taken orally?
…………………………………………………………………………………….
Activity 13 1. Psychotherapeutic medicines can be classified into stimulant, antidepressant and antipsychotic. For each group in the classification, a) State its function
b) Give one example c) Give one side effect.
Psychotherapeutic medicines
Function Example Side effect
Stimulant
Antidepressant
antipsychotic
2. Suggest one proper way to manage each of the following chemicals.
Figure 3.1 List all the food additives used in the sardines. ……………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………………………………………………………………………………… 4. To which type of food additives does each of the ingredients mentioned in (a) belong? ………………………………………………………………………………………………. ………………………………………………………………………………………………. Activity 14
1 a) Diagram 1.1 shows a ginger plant. Ginger can be used as a traditional medicine.
i) Which of the parts P, Q, R or S is used as the main source of medicine? Mark ( ) for your answer in the box provided in Diagram 1.1
ii) What illness can be cured by using ginger?
……………………………………………………………………………………… iii) How is ginger used to treat the illness in 1 (a) (ii)?
b) Table 1.1 shows the functions of three types of medicine.
Functions
Type of medicine
Prevents pain Kills or prevents the reproduction of bacteria. Changes the emotions and behavior of the patient.
X: ………………………………. Y………………………………… Z: ……………………………….
Table 1.1 i) Complete Table 1.1 to show which medicines have the functions given in the table. ii) What is the side effect of medicine of type X if it is used by a child of less than 2 years? ……………………………………………………………………………………………….. iii) A patient treated by medicine of type Y must complete all the supply given by the doctor in order to make sure all the bacteria are killed. What will happen if not all the bacteria is killed? ……………………………………………………………………………………………………. iv) Tranquilizer is an example of medicine of type Z. Give one change that might happen to a patient’s emotions when treated using this medicine. …………………………………………………………………………………………………….