7/17/2019 Modul Chemistry Form 4 http://slidepdf.com/reader/full/modul-chemistry-form-4 1/131 Modul Chemistry Form 4 [email protected]1 CHAPTER 2: THE STRUCTURE OF ATOMA MATTERActivity 1Fill in the blanks with suitable word(s) in the box given 1. Matter is made up of ………………………. and …………………… particles. 2. The tiny particles may be atoms ……………….. and ……………………….3. An atom is the ………………… particle of an element that can …………………….. in a chemical reaction. 4. A molecule is a group of two or more …………………… which are …………………… bonded together. 5. An ion is a …………………………………. or negatively – charged particle 6. Diffusion occurs when particles of a substance move ……………… between the particles of another substance. 7. Diffusion of matter occurs most rapidly in ………………… state, slower in ………………….. state and slowest in …………………….. state. This is due to the different ……………………… and ………………………. of particles in the three states of matter. 8. Matter consists of small particles that always collide among each other. The particles move faster when energy is …………………… and the particles move slower when the energy is ….………………..….Learning Outcomes You should be able to: describe the particulate nature of matter, state the kinetic theory of matter, define atoms, molecules and ions, relate the change in the state of matter to the change in heat, relate the change in heat to the change in kinetic energy of particles, explain the inter-conversion of the states of matter in terms of kinetic theory of matter. Ions tiny molecules discrete smallest take part positively-charged in released atoms gas chemically solid absorbed different arrangement movement liquid
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4. Complete the passage below by using the words given below.(solid, gas, boiling point, melting point , solid, gas, liquid , intermolecular , released,absorbed, overcome )
The temperature at which a ………………………………… completely changes to a liquid
is called ……………………………… Boiling point is the temperature at which
a…………………… changes into …………….. . During the boiling process, the
temperature remains constant because the heat energy is …………………… by theparticles and is used to …………………...………………… the ……………………………
forces between particles.
5. The graph below shows the change in temperature with time when a matter in solid statewas heated.
a positively-charged particle in an atom. The central region of atom has a very smallpositively-charged …………………..…,which contains almost all the mass of theatom.
Bohr’s atomic model proposed by
……………………in1913
The electrons in an atom move in………..……… around the nucleus whichcontains protons.
Chadwick proved the existence of……………….., the neutral particle in thenucleus. The nucleus of the atom contains protons &neutrons, and the nucleus is surrounded byelectrons.
Activity 4
Fill in the blanks and complete the table.1. Atoms are made up of subatomic particles namely protons, …………… and …………..
2. ………………………and …………….. are found in the nucleus of an atom while electrons
surround the nucleus.
3.Subatomic particle Symbol Relative mass Relative electric charge
Proton
Neutron
Electron
4. The proton number of an element is the number of ………………… in its atom.
Proton Number, Z = Number Of Proton
5. Protons and neutrons are collectively called nucleons.
The nucleon number of an element is the total number of ………………….. and
4. What is the volume of 24 g methane ,CH4 at STP?[Relative atomic mass: H, 1; C, 12. Molar volume: 22.4 dm 3 mol-1 at STP]
(Ans: 33.6 dm3)
5. How many aluminium ions are there in 20.4 g of aluminium oxide, Al2O3?[Relative atomic mass: O, 16; Al, 27. Avogadro constant, N A: 6.02 x 1023 mol-
(2 x 0.2 x 6.02 x1023
)
6. Calculate the number of hydrogen molecules contained in 6 dm3 of hydrogen gas at
room conditions.[Molar volume: 24 dm3 mol-1 at room conditions Avogadro constant, N A: 6.02 x 1023 mol-1]
(Ans: 1.505x1023
molecules)
7. Find the volume of nitrogen in cm3 at STP that consists of 2.408 x 1023 nitrogenmolecules.
[Molar volume: 22.4 dm3 mol-1 at STP. Avogadro constant, N A: 6.02 x 1023 mol-1]
1. state the meaning of chemical equationidentify the reactants and products of a chemical equation
2. write and balance chemical equations3. interpret chemical equations quantitatively and qualitatively4. solve numerical problems using chemical equations5. identify positive scientific attitudes and values practiced by scientist in doing research6. justify the need to practice positive scientific attitudes and good values in doing researsh7. use chemical equations for easy and systematic communication in the field of chemistry.
Activity 13 (refer text book pg 48)
Example: C (s) +2
O (g) 2
CO (g)
Reactant product
1) Qualitative aspect of chemical equation:
a) Arrow in the equation the way the reaction is occurring
b) Substances on the left-hand side ……………………..
c) Substances on the right-hand side ………………………
d) State of each substance ………: (s), ………………(l ), gas ……….and aqueous
solution ……………….
2) Quantitative aspect of chemical equations
Coefficients in a balanced equation the exact proportions of reactants and products in
To Investigate The Chemical Properties of Lithium, Sodium & Potassium
1) The Reaction of alkali metals with water, O H 2
Problem Statement: How does the reactivity of Group 1 elements change when theyreact with
water?
Hypothesis: When going down Group 1, alkali metals become more reactive intheir reactions
with water.
Variables: Manipulated variable – Different types of alkali metalsResponding variable – Reactivity of metals with waterFixed variables – water, size of metals
a) Write the procedure to carry out this experiment. (refer to practical book pg 39)
b) Complete this table (Data & Observation )
Alkali metal Observation Lithium
Sodium
Potassium
2) The Reaction of alkali metals With Oxygen, O2
(This procedure can also be used to test the reaction of alkali metals with chlorine gas!)
b). In gaseous state they react with hot iron to form a brown solid, iron (III) halides.
Example: Fe2 +2
3 Br 3
2 FeBr
Write a balanced equation when iodine vapour reacts with iron
…………………………………………………………………………………………
c). Group 17 elements react t with sodium hydroxide solution, NaOH , to form
sodium halide, sodium halate (I) and water
Example:2
I + NaOH 2 NaI + NaOI + O H 2
Write a balanced equation when chlorine reacts with sodium hydroxide solution
…………………………………………………………………………………………
5)The reactivity of Group 17 elements decreases when going down the group. Explain why.
a) When going down the Group 17 atomic size …………………………….. b) The outermost occupied shell becomes …………………. from the nucleus. c) Therefore the strength to attract one electron into the outermost occupied
shell by the nucleus becomes ………………………
6) Chlorine gas reacts more vigorously with hot iron as compared to bromine gas. Explain(Proton number: Cl, 17 ; Br, 35)
…………………………………………………………………………………………………
………………………………………………………………………………………………… Activity 8
To investigate the Chemical properties of Group 17 elements.
The Reaction of halogens with iron (refer practical book pg 44)
1) Data and Observation (Complete the following table)
2 Draw the electron arrangements for the formation of the following covalent compounds[Proton number : C, 6 ; Cl, 17, : O, 8](a) Tetrachloromethane, CCl 4
(b) Carbon dioxide molecule, CO2
3 Complete the table below to compare the characteristics for the formation of ionic and covalentbonds.
Ionic bond Characteristic Covalent bondValence electrons
Electrons involved
Elements Non-metals atom and non metal atoms
Electron transfer to achievestable electron arrangement
Bond formation
Particles
D PROPERTIES OF IONIC AND COVALENT BONDING
Learning outcomesYou should be able to:
list the properties of ionic compounds.
list the properties of covalent compounds
explain the differences in the electrical conductivity of ionic and covalent compounds
describe the differences in melting and boiling points of ionic and covalent compounds
compare and contrast the solubility of ionic and covalent compounds
state the uses of covalent compounds as solvents.
Activity 7 : Physical properties of ionic and covalent compounds
1. Complete the table of the properties of ionic and covalent compounds, using the wordsgiven in the box :
conduct electricity in aqueous solution or molten state do not conduct electricitylow solid high insoluble soluble solid, liquid,
(a) Construct a table to show the information of the three elements in terms of
The number of protons
The number of neutrons
The electron arrangement
The number of valence electrons [4 marks]
Answer:
(b) The reaction between atoms of element G and W forms an ionic compound whereas thereaction between atoms of element E and W forms a covalent compound.Explain how these ionic and covalent compounds are formed.
( c) The ionic compound formed from the reaction between atoms of element G and W doesconduct electricity when it is in solid state but can conduct electricity when dissolved in
water.
Describe an experiment to investigate this property.[8 marks]
5. Ionic compounds in molten state or in aqueous solution are electrolytes while covalentcompounds and ionic compounds in solid state are non-electrolytes. Metals are non-electrolytes but are good conductors of electricity.
Classify the substances in the text box below into electrolyte and non-electrolyte
Activity 21. What do you understand by the term electrolysis?
Electrolysis is a process whereby compounds in (a) .................... or (b) ..……………states are broken down (or decomposed) into their constituent (c) …………………… by
passing (d) ……………………. through them.
2. Anode is the electrode which is connected to the (e) …………………. terminal of abattery.
3. Cathode is the electrode which is connected to the (f ) ……………………… terminal of abattery.
4. Carbon or platinum is chosen as electrodes as they are chemically inert or unreactive.5. The diagram below shows the set-up of apparatus of electrolysis of molten lead(II)
bromide. Name the main apparatus and materials in the diagram.
Activity 31. Diagram 3.1 shows the relationship between the presence of freely moving ions and
electrical conductivity.The box below shows a list of statements that explain the why ionic compound in solid
state do not conduct electricity but will conduct electricity in aqueous solution. Thestatements are arranged in random order.Choose the correct statement from the box below and write it into the correct text box inDiagram 3.1.
During electrolysis cations are attracted to the cathode and anions are attracted to the anode.
Solid sodium chloride contains sodium ions and chloride ions which are in fixed position andnot freely moving.
In solid state, sodium ions and chloride ions are strongly attracted by electrostatic forces in alattice.
Electric circuit is complete due to the flow of electrons along the connecting wires and
movement of ions in the solution. If the electrodes are placed further apart, the ammeter reading will decrease because there
will be an increase in internal resistance.
Aqueous sodium chloride contains freely moving ions to conduct electricity.
Learning Outcomes:You should be able to:
describe electrolysis,
describe electrolytic cell, identify cations and anions in a molten compound,
describe evidence for the existence of ions held in a lattice in solid state but move freely inmolten state,
describe electrolysis of a molten compound,
write half-equations for the discharge of ions at anode and cathode,
predict products of the electrolysis of molten compounds.
2. Colour all the cations red and the anions blue in solid sodium chloride and in theelectrolyte in Diagram 3.1 above.
Activity 4
1. Given below is a list of ionic compounds in molten state. Identify the cation and anion ineach electrolyte.
Electrolyte (Molten)
Cation Anion Name Formula Name Formula
Sodium chloride
Lead(II) oxide
Potassium bromide
2. Given below is a list of electrolytes and products discharged at both electrodes. Basedon the given substance discharged at the electrode, write a half equation to represent
the reaction occurring at the electrode.
Electrolyte (molten)
Substance discharged at the electrodes and the half equation
Activity 51 The flow chart below is used to predict the products formed at the electrodes during the
electrolysis of molten lead(II) bromide.
2. In the spaces below, draw a similar flow chart (as in question 1) to predict the productsformed at the electrodes from the electrolysis of molten zinc chloride, ZnCl2.
Learning Outcomes:You should be able to: identify cations and anions in an aqueous solution, describe the electrolysis of an aqueous solution, explain using examples factors affecting electrolysis of an aqueous solution, write half equations for the discharge of ions at the anode and the cathode, predict the products of electrolysis of aqueous solutions.
Activity 6
1. State three factors that may influence the selective discharge of ions during theelectrolysis of an aqueous solution.
(a) …………………………………………………………………………………………………
(b) ………………………………………………………………………………………………….
(c) ………………………………………………………………………………………………….
2. In an aqueous solution of sodium chloride, apart from sodium ions, Na+ and chloride
ions, Cl-- , ………………………ions, ……… and ……………………………….ions, ……
from the slight dissociation of water are also present.
3. List the electrochemistry series (cations and anions) in order of increasing ease ofdischarge.
Ease of discharge increases
Cation: …………………………………………………………………………………………….
Anion: ……………………………………………………………………………………………..
4. The following statements refer to the factors that affect the electrolysis of an aqueoussolution. Fill in the blanks.
(a) The ions that are placed …………………… in the electrochemical series will be
……………….. discharged. (b) If the concentration of a particular ion is …………………, the ion is ……………..
………………………
(c) In the electrolysis of copper(II) sulphate, CuSO4 ……………..using copper
electrodes, no ions are discharged at the anode. Instead, the copper anode
Activity 7The diagram below shows the set-up of apparatus of an electrolytic cell containingconcentrated copper(II) sulphate solution. Two test tubes filled with copper(II) sulphatesolution were placed over the electrodes J and K to collect any gas evolved. The switch isthen turned on so that electrolysis of copper(II) sulphate solution can occur.
(a) Identify the cations and the anions present in the aqueous solution.
(a) The table below shows two electrolytic cells with electrolytes of differentconcentration. You are required to answer each section by writing your answer inthe spaces provided.
1. In the diagrams, label the cathode
with the symbol “” and theanode with the symbol “+”.
2. Show the direction of the flow of theelectrons with arrowheads, “ > “
3. Write the formula of all ions in theelectrolyte.
4. a. Write the formula of ions which areattracted to the cathode.
b. Underline the formula of ion whichis selectively discharged.
c. State the factor that affect theselective discharged of ion
5. Write the half equation to representthe reaction at the cathode.
6. What will you observe at thecathode?
7. a. Write the formula of ions which areattracted to the anode.
b. Underline the formula of ion whichis selectively discharged.
c. State the factor that affect theselective discharged of ion
8. Write the half equation to representthe reaction at the anode.
(b) The table below shows two electrolytic cells with the same electrolytes withdifferent electrodes. You are required to answer each section by writing youranswer in the spaces provided.
1. In the diagrams, label the cathode
with the symbol “
” and theanode with the symbol “+”.
2. Show the direction of the flow of theelectrons with arrowheads, “ > “
3. Write the formula of all ions in theelectrolyte.
4. a. Write the formula of ions whichare attracted to the cathode.
b. Underline the formula of ionwhich is selectively discharged.
c. State the factor that affect theselective discharged of ion
5. Write the half equation to representthe reaction at the cathode.
6. What will you observe at thecathode?
7. a. Write the formula of ions whichare attracted to the anode.
b. Underline the formula of ionwhich is selectively discharged.
c. State the factor that affect theselective discharged of ion
8. Write the half equation to representthe reaction at the anode.
Learning Outcomes:You should be able to: state uses of electrolysis in industries, explain the extraction, purification and electroplating of metals involving electrolysis in industries, write chemical equations to represent the electrolysis process in industries, justify uses of electrolysis in industries,
describe the problem of pollution from electrolysis in industry .
Activity 9
1. Fill in the blanks.
The application of electrolysis in industries are (a) ……………………………………….
(b) ……………………………………………… and (c) ……………………………………
In the extraction of aluminium from its ore, (d) ….……………… electrodes are used
and (e) ……..………………. is added to aluminium oxide to lower its melting point.
In purification of metals, the pure metal is made the (f) ….………………. and the
impure metal is made the (g) ……….……………. The electrolyte used is an aqueous
salt solution of the metal ions.
In electroplating of metals, the (h) ………..…………….is made the anode and the (i)
……………… to be (j) ..…..………………….. is made the cathode. The electrolyte
used is an aqueous salt solution of the electroplating metal.
The purposes of electroplating metals are to make the electroplated object more (k)
………………………………….. and (l) …………………..……………… to corrosion.
2. Below are shown the three uses of electrolysis in industries. Fill in the blanks.
4. The diagram below shows an example of a simple voltaic cell.
In the text box below are sentences explaining the production of electricity from a simplevoltaic cell. The sentences are listed in random order. You are required to arrange thesesentences in the best possible order so as to give a clear description of the reactionsoccurring in a simple voltaic cell.
[If you have any problem, you can refer to page 104 of the text book for guidance.]
Answer:
(a) ………………………………………………………………………………………………………
………………………………………………………………………………………………………
(b) ………………………………………………………………………………………………………
………………………………………………………………………………………………………
(c) ……………………………………………………………………………………………………..
………………………………………………………………………………………………………
An example of a simple voltaic cell is a magnesium strip and a copper strip immersed indilute sodium chloride solution.
The electrons then flows from the magnesium ribbon to the copper plate through the wireand this results in the flow of electrical current.
Hence magnesium atom releases electrons more easily than a copper atom and themagnesium act as the negative terminal of the cell.
The overall equation for the reaction is given as follows.Mg(s) + 2H+(aq) Mg2+(aq) + H2(g)
Magnesium is placed higher than copper in the electrochemical series.
At the negative terminal, each magnesium atom releases two electrons and the Mg2+ formed moved into the solution.
Mg(s) Mg2+ (aq) + 2e
At the positive terminal which is the copper plate, the electrons are accepted by the H+ ions in sodium chloride solution.
2. The table below listed are five types ofvoltaic cells commonly used in our dailylives. Each voltaic cell has its advantagesand disadvantages. Complete the table bystating the advantages and disadvantagesof each voltaic cell.
Voltaic cell Advantage
s Disadvantage
s 1. Lead-acidaccumulator
2. Dry cell
3. Mercurycell
4. Alkalinecell
5. Nickel-cadmiumcell
Activity 12What are the differences between an electrolytic cell and a voltaic cell?Table 12.1 are statements showing differences between an electrolytic cell and a voltaic cell.Complete Table 12.2 by choosing the correct matching statements.
It does not require a source of electriccurrent
It requires a source of electric current
The electrical energy causes chemicalreactions to occur at the electrodes. Electrical energy chemical energy
The chemical reaction that occur at theelectrodes produces electric current.Chemical energy electrical energy
The electrodes must be of two differentmetals
The electrodes may be of the same materialsuch as carbon
Electrons flow from the positive electrode(anode) to the negative electrode (cathode).
Electrons flow from the more electropositivemetal (negative terminal) to the lesselectropositive metal (positive terminal).
Ions receive electrons at the positiveterminal. (Reduction)
Ions donate electrons at the positive terminal.(Oxidation)
Ions receive electrons at the negativeterminal. (Reduction)
Ions donate electrons at the negativeterminal. (Oxidation)
Learning Outcomes:You should be able to: describe the principles used in constructing the electrochemical series, construct the electrochemical series, explain the importance of electrochemical series, predict the ability of a metal to displace another metal from its salt solution, write the chemical equations for metal displacement reactions.
Activity 13 Three experiments were conducted to investigate the potential differences between three pairs ofmetals in a voltaic cell. An electrochemical series for four metals P, Q, S and T is then constructedbased on the potential difference obtained. Three pair of metals used as electrodes in different voltaiccells are: P and Q, Q and S and S and T. All the metals are cleaned with sandpaper before used.50 cm3 of 1.0 mol dm-3 sodium nitrate solution is poured into a beaker as electrolyte.
Experiment I
The electrodes P and Q are immersed into the solution. The two electrodes are connected to avoltmeter using copper wires. Electrode Q is the positive terminal. The voltmeter reading isrecorded.
Experiment IIThe electrodes Q and S are immersed into the solution. The two electrodes are connected to avoltmeter using copper wire. Electrode Q is the positive terminal. The voltmeter reading isrecorded.
Experiment IIIThe electrodes S and T are immersed into the solution. The two electrodes are connected to avoltmeter using copper wire. Electrode T is the positive terminal. The voltmeter reading isrecorded.
Based on Experiment I, II and III, answer the questions below.(a) Record the voltmeter reading of each experiment in the spaces provided.
Experiment 1 Experiment II Experiment III
Voltmeter reading: …………. Voltmeter r eading: …………… Voltmeter reading: ….……..
(b) Construct a table to record the data from the above experiments.
K > Na > Ca > Mg > Al > Zn > Fe Sn > Pb > H > Cu > Ag
2. Example : Ewacrion between xinc and copper(II) sulphate solution
Chemical equation : Zn + CuSO4 ……………… + ………….
…….. is place higher position than ……… in electrochemical series, , …………….. is moreelectropositive than …………….., hence ………….. can displace ……………f rom
………………………. solutions.
Copper(II)sulphatesolution
Zinc atom releases 2 electrons to form zinc ion, Zn2+ : Half equation : ………………….
Copper(II) ion Cu2+ receives 2 electrons to form copper atom : Half equation :……………..
Ionic equation : ……………………………………………………….
3. Experiment : To construct the electrochemical series using the principle of displacement ofmetals (Displacement Reaction)
Problem Statement : ………………………………………………………………………………
………………………………………………………………………………
Hypothesis: The greater the number of metals that can be displaced by a metal fromtheir solutions, the higher is its position in the electrochemical series.
Variables:Manipulated variable : ……………………………………
Responding variable : ………………………………
Fixed variables : ……………………………………
List of Materials and Apparatus:
Test tubes, sand paper, 1 mol dm-3 zinc nitrate solution, 1 mol dm-3 lead (II) nitratesolution, 1 mol dm-3 copper (II) nitrate solution, magnesium strips, zinc strips, leadstrips and copper strips.
1. Pour 5 cm3 of magnesium nitrate solution, zinc nitrate solution, lead (II) nitrate solution, andcopper (II) nitrate solution into four separate test tubes.
2. For each test tube, place a strip of magnesium into each solution.3. Record all the observations.
4. Repeat steps 1 to 3 using strips of zinc, lead and copper to replace the magnesium strip. Foreach repetition, use a fresh salt solution.
Data and Observation
Magnesiumnitrate solution
Zinc nitratesolution
Lead (II) nitratesolution
Copper (II)nitrate solution
Magnesium
Zinc
Lead
Copper
a. Which metal can displace the most number of other metals from their solutions?
…………………………………………………………………………………………….
b. Write the half equation of the reaction occurred in magnesium strip for this experiment.
……………………………………………………………………………………………………
c. Which metal can be displaced by all other metals in the experiment?
…………………………………………………………………………………………………..
d. Arrange the metals in descending order based on the electrochemical series andthe number of metals displaced by it.
……………………………………………………………………………………………………
e. Write the ionic equations to show all displacement reactions by zinc
5 4.0 g of sodium carbonate powder, Na2CO3 , is dissolved in water and made up to 250 cm3.What is the molarity of the sodium carbonate solution? [Relative atomic mass: C, 12; O, 16; Na, 23]
[ Answer: 0.15 mol dm
-3 ]
Activity 11The number of moles of solute, n in a given volume of solution V and the molarity of M can becalculated by using the formula :
n = Number of moles of solute
M = Molarity of solution (mol dm-
) V = Volume of solution (dm3)
If the volume is in cm3 – convert the volume of solution from cm3 to dm3
5 Calculate the number of moles of ammonia in 150 cm3 of 2 mol dm-3 aqueous ammonia.
[ Answer: 0.3 mol ] 6 A student pipetted 20.0 cm3 of potassium hydroxide , KOH solution into a conical flask. The
concentration of the alkali was 1.5 mol dm-3 . Calculate the number of moles of potassium ,KOH in the flask.
[ Answer: 0.03 mol dm-3
]
7 Calculate the number of moles of hydrogen ions present in 200 cm of 0.5 mol dm- sulphuricacid, H2SO4.
2 Preparation of standard solutions by Weighing method (mass of solute) :-
Step 1 : Calculate the mass of solute needed .
mass = n X molar mass
= MV X molar mass 1000
Example: To prepare 100 cm3 of 2.0 mol dm-3 sodium hydroxide solution. Calculate the mass of NaOH needed. [Relative atomic mass: Na, 23 ; O, 16 ; H, 1]
mass = n X molar mass
= MV X molar mass 1000
= 2.0 X 100 X 40 = 8 g1000
Try this :(a) To prepare 250 cm3 of 1.0 mol dm-3 sodium carbonate solution.
Calculate the mass of Na2CO3 needed. [Relative atomic mass: Na, 23 ; O, 16 ; C, 12]
[Answer : 26.50g]
(b) 0.25 mol dm-3 solution of sodium hydroxide was prepared by dissolving x g of sodiumhydroxide in 750 cm3 of water. What is the value of x ? [Relative atomic mass: Na, 23 ; O, 16 ; H, 1]
Add water slowly by using adropper to bring the level of thesolution to the calibration mark.
The volumetric flask is closedtightly and inverted several times toget a uniform or homogenous
solution.
(b)
Calculate the mass of soluteneeded.
Weigh out the exact mass of soluteneeded in a weighing bottle.
Dissolved the solute in a smallamount of distilled water.
(c)
Add more water carefully to thevolumetric flask and swirl gently.
Shake well to ensure thoroughmixing.
(d)
Activity 13 : Preparation of Standard solutions by Dilution method
1 Dilution method
Step 1 : Calculate the volume of stock solution required by using the equation:-
M1 = molarity of solution before dilutionV1 = volume of solution before dilutionM2 = molarity of solution after dilutionV2 = volume of solution after dilution
Example: 50 cm3 of 0.1 mol dm-3 sodium hydroxide, NaOH solution from 2.0 mol dm-3
sodium hydroxide,NaOH solution
Before dilution After dilution M1 V1 M2 V2
2.0 mol dm-3 ? 0.1 mol dm-3 50 cm3
2.0 x V1 = 0.1 x 50 V1 = 0.1 x 50 = 2.5 cm3
2.0
Try this : 100 cm of 0.5 mol dm- potassium manganate(VII) ,KMnO4 solution is preparedfrom 1.0 mol dm-3 potassium manganate(VII) ,KMnO4 solution. Calculate the volume of thesolution
M1V1 = M2V2
When using the equation M1V1 = M2V2 , make sure that both V1 and V2 are ofthe same unit.
…………………………………………………………………………………………………. 2 What is the function of an indicator?
…………………………………………………………………………………………………..
3 Complete the table below.
Indicator Colour in solution
Acid Neutral Alkali Red litmus paper
Blue litmus paper
Phenolphthalein
Methyl orange
4 Write out the procedure for carrying out an acid-base titration to determine the volume ofnitric acid 0.5 mol dm-3 needed to neutralise 25 cm3 potassium hydroxide 0.5 mol dm-3 .Label the diagram.
Useful equations in solving numerical problems involving neutralisation.:
n = no of moles
M = Molarity of solution V = Volume of solution in dm3
Ma = molarity of acid Mb = molarity of alkali Va = volume of acid Vb = volume of alkali
a and b = mole ratio of acid to alkali in a balanced chemical equation
Example:
In an experiment, 25 cm3 of sodium hydroxide solution, NaOH of unknown concentrationrequired 26.50 cm3 of 1.0 mol dm-3 sulphuric acid, H2SO4 for complete reaction in titration.Calculate the molarity of sodium hydroxide.
Write out a balanced chemical equation:
H2SO4 + 2NaOH Na2SO4 + 2H2O a = 1 mol b = 2 mol
MaVa 1MbVb = 2
,1.0 X 26.50 = 1
Mb X 25.00 2
Mb = 2 X 1.0 X 26.50 = 2.12 mol dm-3(Molarity of sodium hydroxide)
25.00
1 What is the volume of 1.5 mol dm-3 aqueous ammmonia required to completely neutralise30.00 cm3 of 0.5 mol dm-3 sulphuric acid ?
2 Calculate the volume in cm3 2.0 mol dm-3 hydrochloric acid that is required to reactcompletely with 2.65 g of sodium carbonate. [Relative atomic mass: Na, 23 ; O, 16 ; C, 12]
[ Answer: 25 cm3]
3 25 cm3 of sulphuric acid was neutralised with 18.0 cm3 of sodium hydroxide 1.0 mol dm-3. Calculate a) the number of moles of sulphuric acid that is used in this reaction.
b) the molarity of sulphuric acid
[Answer (a) 0.009 mol (b) 0.36 mol dm-3 ]
4 24 cm3 of 0.1 mol dm-3 NaOH is required to completely neutralise 20.0 cm3 of sulphuric acid.Calculate the concentration of sulphuric acid in (a) mol dm-3 (b) g dm-3
5 What is the molarity of phosphoric acid if 15 cm3 of the acid is neutralized by 38.5 cm3 of 0.15mol dm-3 NaOH ?
[Answer (a) 0.218 mol dm-3 ]
Activity 18
1 A student carried out an experiment to determine the end-point for the titration of25.0 cm3 of 1.0 mol dm-3 sodium hydroxide solution with hydrochloric acid. Phenolphthalein isused as the acid-base indicator.Table 1 shows the three titrations that were conducted and the magnification of the burettereadings.
(a) Record the burette readings for the three titrations in the space provided in Table 1.
(b) Construct a table and record the initial burette reading, final burette reading and the volume of acid used for each titration.
(c) Calculate the average volume of hydrochloric acid used in the experiment.
(d) Calculate the concentration of hydrochloric acid used in the experiment.
(e) If the experiment is repeated by replacing 1.0 mol dm- of hydrochloric acid with 1.0 moldm-3 of sulphuric acid, predict the end-point of the titration.
………………………………………………………………………………………………….
(f) Acids can be classified into strong acid and weak acid. Classify the following acids into strong acids and weak acids.
state examples of salts used in daily life, explain the meaning of salt identify soluble and insoluble salts, describe the preparation of soluble salts, describe the purification of soluble salts by recrystallisation, list physical characteristics of crystals, describe the preparation of insoluble salts, write chemical and ionic equations for reactions used in the preparation
of salts, design an activity to prepare a specified salt, construct ionic equations through the continuous variation method solve problems involving calculation of quantities of reactants or products in stoichiometric reactions
Activity 1 : Meaning and uses of Salts
1. A salt is an ……………………..……… formed when the ……………….. ion, from an ……………
Iron sulphate FeSO4 Paint for yellow line on road Ammonium nitrate NH4NO3 X-ray ‘meals’ in hospitalCopper(II) sulphate CuSO4 Nitrogenous fertilizer Sodium chloride NaCl Toothpaste
Sodium hydrogen carbonate Iron tablets, for anaemiapatient
5. Rewrite each of the following chemical equation as ionic equation. Shown below is an examplewhere a chemical equation can be simplified into an ionic equation.
Example : Chemical equation : Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g)
Activity 8 : Construct ionic equation for the formation of lead(II) chromate through thecontinuous variation method,
Figure 1
Figure 1 shows seven test tubes for the reaction between lead(II) nitrate Pb(NO3)2 0.5 mol dm-3 andpotassium chromate(VI) K2CrO4 0.5 mol dm-3.
(a) Calculate the number of moles of lead(II) nitrate Pb(NO3)2 and potassium chromate(VI) K2CrO4 used in test tubes 1-7. Using a ruler, measure the height of lead(II) chromate(VI) precipitateformed. Record all these in Table 1as well as complete Table 1.
Activity 9 : Solve problems involving calculation of quantities of reactants or products instoichiometric reactions
Example 1 : A student prepares copper (II) nitrate by reacting copper (II) oxide with 100 cm3 1.5 mol dm-3 nitric acid. Calculate the mass of copper (II) oxide need to reactcompletely with the acid. [Relative atomic mass: Cu, 64 ; O, 16]
Number of moles of HNO3 = 1.5 x 100 = 0.15 mol1000
Mole ratio of CuO : HNO3 = 1 : 2
Number of mole of CuO = 1 x 0.15 = 0.075 mole
2Mass of CuO = 0.075 x (64 + 16) = 6 g
Question :1 Excess zinc powder is added to react completely with 50
3cm of 2.0
3
dmmol hydrochloric acid.
(a) Write an ionic equation for the reaction between zinc and hydrochloric acid.
(b) Calculate the number of moles of hydrochloric acid used.
(c) Calculate the volume of hydrogen gas liberated at room conditions.
[Molar volume: 2413
mol dm ]
2 Excess of magnesium carbonate powder, MgCO3, is reacted with 100 cm3 of a 1 mol dm-3 sulphuric acid H2SO4 ,
What is the mass of magnesium sulphate formed?[Relative atomic mass : Mg =24, O=16, S = 32 ]
3. 0.12 g of magnesium reacts with excess hydrochloric acid to produce hydrogen gas. Given thatthe relative molecular mass of H=1, Mg = 24, CI =35.5 and 1 mol of gas occupies 24 dm3 at roomtemperature and pressure.Fnd the (a) mass of salt formed (b) volume of gas produced
Learning OutcomesYou should be able to: state examples of salts used in daily life, explain the meaning of salt identify soluble and insoluble salts, describe the preparation of soluble salts, describe the purification of soluble salts by recrystallisation, list physical characteristics of crystals, describe the preparation of insoluble salts, write chemical and ionic equations for reactions used in the preparation
of salts, design an activity to prepare a specified salt, construct ionic equations through the continuous variation method solve problems involving calculation of quantities of reactants or products in stoichiometric reactions
Activity 10 : Qualitative Analysis
1. Qualtitative analysis of a salt is a chemical technique used to identify the …….. that are present
in a salt by analysing its ………………. and ……………………. properties.
2. Make inferences on the following substances based on their colour: (use formula of substance whenwriting your answer. Make it is correct!)
Colour (solid or solution) Substance or cation or anion Green powder Salt: Cation Blue powder Cation:
Brown powder Cation:
Black powder Two metal oxides:Yellow powder when hot and white whencold Brown powder when hot and yellow whencold Blue solution Cation: Pale green solution Cation: Brown solution Cation: Solid : White Solution : colourless
Activity 13 : Action of Heat On Nitrate SaltsNitrates Salts - Decompose on heating liberate nitrogen dioxide gas and oxygen gas except NaNO 3 and KNO3 which liberate oxygen gas only
Activity: Complete the chemical equation and observation for the action of heat on nitrate salt
Nitrate salts Action by Heat
Metal Nitrate metal nitrite + oxygen
Potassium nitrate2KNO3 2 KNO2 + O2
Observation : white solid formed, gas released relighted glowingsplinter
(A). Conclusion for salt S1 : …………………………………………………………………….
(B). Identify the salt S2The following tests were carried out on an aqueous solution of salt S2. Based on theobservations given for each test, state its inference. Finally, identify salt S2.
Test Observation Inference
1. Pour about 2 3cm of S2
into a test tube. Add
NaOH solution until excess
White precipitate,dissolve in excessNaOH solution
2. Pour about 2 3cm of S2
into a test tube. Add
3 NH solution until excess
White precipitate,dissolve in excessammonia solution
Activity 18 : plan qualitative analysis to identify anions
Rajoo works in a laboratory. He noticed that there are two large bottles. However both the labelshave fallen off. He found four labels beside the bottles. i.e ‘Sodium Chloride Solution’, ‘SodiumCarbonate Solution’, ‘Sodium Sulphate Solution’ and ‘Sodium Nitrate Solution’. So he has to carry outconfirmatory test to identify the anion in both the solutions.
Complete the graphic organizers describing four tests and their results. The charts can then be usedby Rajoo to distinguish which bottle contains which solution.
2. A pure metals contains atoms of the same size arranged in a regular and orderly
manner . Pure metal are ……………………………….. and ……………….……………because the layers of atom……………………………………………when external force isapplied on them.
3. In an alloy, the foreign metal atoms ………………………. …………...arrangement ofmetal
atoms and the layers of metal atoms are prevented from …………......over each othereasily.4. Complete the sequences by drawing the arrangement of atoms in the box below.
+
5. Three aims of alloying a pure metal are :
a. to increase the …………………………. and ……………………….. of metal.b. to prevent ……………………………… or rusting.c. to improve the …………………………. of metal surface.
1. Main composition of glass is ………………………………, (SiO2).
2. Complete the table below.
Type of glass Chemical
composition
Properties Examples
of uses(a)
………………………. Silica 99%Boron oxide1%
Very high softening point(1700oC).Transparent to ultra violet andinfra red light.Difficult to be made intodifferent shapes.Does not crack with suddentemperature change.Very resistant to chemicalattack.
Low softening point (700oC).Breaks easily.Cracks easily with suddentemperature changes.Less resistant to chemicalattack.Easy to make into differentshapes.
Bottles,Window,Light bulb,Bowl
(c)
……………………….
Silica 80%Boron oxide
15%Sodiumoxide 3% Aluminiumoxide 1%
High softening points(800oC).Does not crack easily with
sudden temperature change.Transparent to ultra violetlight.Very resistant to chemicalattack.
chemical stability,Less susceptible tointerference.
Transmit data, voice
and image in adigital format.
Fibre glass
(vi)………………….. …………………..…………………..
High tensile strength,Easy to colour,Low in density,Very strong.
(vii)…………………..………………….. ……………………
Photochromicglass
(viii)…………………..…………………...
…………………..
When it is exposed to light,silver chloride is converted
silver and darken the glass
(ix)………………….. …………………..
………………….. Activity 9
1. (a) Bronze is an alloy of copper.(i) Name the element that is added to copper to form bronze.…………………………………………………………………………………. .[1 mark] (ii) Explain why bronze is harder than pure copper.……………………………………………………………………………………………. ………………………………………………………………………………….. [2 marks] (iii) Draw and label the arrangement of particles in pure copper and bronze.
Pure copper Bronze [2 marks](b) Synthetic polymers are widely used in our daily lives.
(i) Complete the table with the correct monomers.
Polymer Monomer
Polyvinylchloride
Polyethene
[2 marks](ii) State one example of polyvinylchloride commonly used n our daily lives.
(e) Write a chemical equation when sulphur dioxide reacts with rain water.
………………………………………………………………………………………………. [1 mark ]
3 A student conducts an experiment to study the hardness of two metallic plates,R and S. He drops a steel ball on R a few times and each time, the diameter ofthe dent is measured. He repeats the same procedure on the S plate. Thereading of the diameter of the dents made on each metallic plates are asfollows,
Plate
Diameter of dent made (mm)
I II III Average sizeR 2.4 2.3 2.3
S 3.1 3.2 3.2
(a) Write the average size of the dents made by R and S in the table above.[ 2 marks]
(b) What are the differences seen in the two types of metallic plates based on their
(i) properties ………………………………………………………………………… (ii) composition………………………………………………………………………
[ 4 marks]
(c) From the observation made in the given table above, which plate would bemade of
(i) iron? ………………………………………………………………………… (ii) steel? …………………………………………………………………………
[ 2 marks]
The combustion of petrol in the engines of vehiclesproduce sulphur dioxide. This gas when dissolved