Final Exam Ausmat 22 2010 Answer

Name: ___________________________

Group: __________________________

Lecturer: _________________________

Thursday 4 November2 p.m

Time: 2 hours

Examination material: A 15- pages question booklet (4 questions)

Approved dictionaries and calculators may be used

Instructions to Candidates

1. You will have 10 minutes to read the paper. You must not write in your question booklets during this reading time but you may make notes on the scribbling paper provided.

2. You will be expected to extract information such as atomic number and relative atomic mass from the periodic table on the last page. You may remove the page from this booklet before the test begins.

3. Answer all parts of Questions 1 to 4 in the spaces provided in the booklet. You may write on page 15 if you need more space.

4. There is no need to fill all of the space provided; clearly written, well-expressed answers are required. If you delete part or all of an answer you should clearly indicate your final answer.

5. The total mark is 80. The four questions are of approximately equal value.

6. Write your name, group number and lecturer name in the box provided.

2010 CHEMISTRY

AUSTRALIAN MATRICULATION PROGRAMME END OF SEMESTER 1 EXAMINATION

AUSMAT 22

STUDENT’S DECLARATION ON THE USE OF CALCULATORS

By signing the examination attendance roll I declare that: my calculators have been cleared of all memory; no external storage media are in use on these

calculators.

I understand that if I do not comply with the above conditions for the use of calculators I will: be in breach the rules; have my marks for the examination cancelled or

amended; be liable to such further penalty, whether by exclusion

QUESTION 1

(a) Oxides of sulfur and nitrogen are major pollutants that contribute to the formation of acid rain in industrialised country.

(i) State whether sulfur has a low, an intermediate or a high electronegativity.

High (1 mark)

(ii) Draw the shape of SO2 molecule according to VSEPR theory.

-1 marks if no lone pair(2 marks)

(iii) NO2 reacts with rainwater to form acid rain that lowers the pH of rainwater to levels below 5.6. Write an equation for this reaction.

CO2 + H2O H2CO3

1 mark for balanced equation1 mark for formula

(2 marks)

(iv) Calculate the concentration of nitric acid in a rain sample of pH 4.5 if all the hydrogen ions in the sample are due to the presence of nitric acid.

pH = - log [H+][H+] = antilog pH = 3.16 x 10-5 mol L-1

(2 marks)

(v) With the aid of an equation, briefly describe the effects of acid rain towards limestone building.

Buildings made from limestone can be readily attacked by acid rain. The insoluble carbonates can be converted into soluble sulphates or nitrates in the

acid rain. The surface of the buildings will end up looking like it has been eaten away. CaCO 3 + H2SO4 CaSO4 + CO2 + H2O OR CaCO3 + 2 HNO3 Ca (NO3 ) 2 + CO2 + H2O

3 marks for explanation 1 mark equation.

(4 marks)

(b) The diagram below shows the action of a catalytic converter in a motor vehicle:

Air

NO N2

CO Catalytic converter CO2

Unburnt hydrocarbons H2O

engine emitted to the atmosphere

Many reactions occur in the catalytic converter. Explain why the reduction of nitric oxide in motor vehicle using catalytic converter is accompanied by a reduction in carbon monoxide levels.

In catalytic converter, carbon monoxide is oxidized to carbon dioxide Simultaneously, carbon monoxide also react with nitric oxide to produce nitrogen

and carbon dioxide Therefore carbon monoxide levels will decrease

(3 marks)

(c) The reaction between nitric oxide with free radicals in the atmosphere will lead to the formation ozone.

(i) Explain this process and write two appropriate equations regarding this process.

NO react with free radical to form NO2 that can undergo photochemical dissociation and formed nitric oxide and atomic oxygen.

NO 2 + hv NO + O The atomic oxygen can react with molecular oxygen with the presence of stabilising

molecule to form ozone. O 2 + O + M O3 + M *

2 marks explanation2 marks for balanced equations

(4 marks)

(ii) Give two effects of ozone to the human health.

Any two

Coughing

Wheezing

Irritation of the bronchial respiratory system

(2 marks)

TOTAL: 20 marks

QUESTION 2

(a) Nitrogen exists in both inorganic and organic forms and exhibits many different oxidation states.

(i) Write the electron configuration of nitrogen.

1s2 2s2 2p3 (2 marks)

(ii) State two likely oxidation state of nitrogen in its compounds.

+5 OR +3 OR -3 (2 marks)

(iii) Identify the process that converts N2 to NO3- .

Nitrogen fixation (1 mark)

(b) The movement of nitrogen between the atmosphere, biosphere and geosphere in different form is described by the nitrogen cycle. With the aid of equations, explain the formation of NO2 in the nitrogen cycle.

Lighting produces high T/ energy enough to break triple bond of N2 in the

atmosphere

Nitrogen react with oxygen to form nitric oxide

Nitric oxide further react with oxygen to form nitrogen dioxide

NO + O2 NO2

(4 marks)

(c) Some of the processes in the nitrogen cycle are carried out under aerobic conditions. State the products of the aerobic decomposition of the elements given below:

(i) Nitrogen

Nitrate ion (1 mark)

(ii) Phosphorus

Phosphate ion (1 mark)

(d) Photosynthesis and aerobic respiration are two of the processes involved in the carbon cycle. Aerobic

respiration is the process by which plants and animals derive energy from the ‘burning’ of glucose.

(i) Write a chemical balance equation to represent the process of aerobic respiration.

C6 H12 O6 + 6O2 → 6 CO2 + 6 H2O + energy1 mark for balanced equation1 mark for formula

(2 marks)

(e) Carbon dioxide is a greenhouse gas.

(i) Explain the polarity of CO2.

CO2 is a non-polar molecule with polar bond It has symmetrical spatial distribution of atoms about central atom

(2 marks)

(ii) Identify the other two greenhouse gases.

Methane OR CFC OR Ozone OR H2O OR Halocarbon OR SOx Or NOx

(2 marks)

(ii) Describe the action of carbon dioxide in maintaining a steady temperature in the earth’s atmosphere.

Carbon dioxide absorbed the infra-red radiation reradiated from earth. This will release more heat to the atmosphere and warms the earth’s atmosphere. It also provides the atmospheric blanket to warm the earth.

(3 marks)

TOTAL: 20 marks

QUESTION3

(a) Give the systematic name for each of the following compounds according to IUPAC nomenclature.

(i)

3-methyl pentan-2-one (2 marks)

(ii)

4-methyl heptylamine/4-methyl heptanamine(2 marks)

(iii)

4,5 – dimethyl hexan-3-ol (2 marks)

(b) Draw the following compounds

(i) Propyl butanoate

(2 marks)(ii) 2,2,3-trimethylhexane

(2 marks)(c) Draw hydrogen bonding between two ethanoic acid molecules.

Any relevant H-bonding

(2 marks)

Credit will be given for answers to part (d) which shows clearly written, well-expressed ideas, and which present accurate and relevant information in a well-organized, logical manner.

Your answer to part (d) should use clear well express ideas and present information in a logical manner.

(d) The physical and chemical properties of organic compounds relate closely with their functional groups.

By referring the molecules above, predict the secondary interactions that exist between pentane-3-one and between pentanoic acid molecules. Compare the melting point and water solubility for both molecules.

Pentane-3-one

London dispersion forces and dipole-dipole

lower melting point, cannot form the hydrogen bond between its molecule

carbonyl group a part in its structure, cannot form the hydrogen bond with polar water

molecule, not soluble in water

Pentanoic Acid

London dispersion forces and hydrogen bond

higher melting point, can form the hydrogen bond between its molecule

hydroxyl group a part in its structure, form the hydrogen bond with polar water

molecule , soluble in water

* +1 mark for organized essay format, grammatically correct, no short forms, etc.

+1 mark for correct flow of the essay (explain about oleic pentane-3-one first & then pentanoic acid)

(8 marks)

TOTAL: 20 marks

QUESTION 4

(a) In human beings β-carotene is converted into retinal, a molecule essential for vision. The structural formulae of β-carotene and retinal are shown below:

β-carotene

Retinal

(i) Explain why β - carotene is insoluble in water.

β - carotene molecule is non-polar

H2O molecule is polar

Non-polar molecules not attracted to/cannot form H-bonds with H2O molecules (3 marks)

(ii) Solutions of β-carotene and retinal were shaken with Tollens’ reagent. A change was observed in one solution.

(1) Complete the following table to show the observation that would have been made after each compound was tested with Tollens’ reagent.

Observation

β-caroteneNo change/ no silver mirror form

RetinalSilver mirror form

(2 marks)

(2) Identify the functional group that reacts with Tollens’ reagent.

Aldehyde (1 mark)

(3) State the type of reaction that this functional group undergoes with Tollens’ reagent.

Oxidation (1 mark)

(4) Draw the structural formula of the organic product formed from the reaction with Tollens’ reagent.

-1 if COOH

(2 marks)

(b) Naproxen is a type of Non Steroidal Anti Inflammatory Drug (NSAID). It is known to be able to reduce inflammation, fever and arthritis pain, similar to aspirin.

Naproxen

(i) Explain why Naproxen is considered to be a weak acid.

It has only carboxyl group with large non-polar part. Low solubility and partial ionization makes Naproxen a weak acid.

(2 marks)

(ii) Use the molecular structure of Naproxen to write a balanced chemical equation for its reaction with carbonate ion, CO3

2-.

(2 marks)

(iii) Explain why Naproxen is insoluble in water at low pH but very soluble in water at high pH.

At low pH, carboxyl group of Naproxen is not ionized, thus non-polar. At high pH, carboxyl turns to carboxylate anion. Polar anion forms stronger ion-dipole interactions with water.

(3 marks)

(c) Compound X, a preservative used in shampoos, has the structural formula shown below:

Compound X

One hydroxyl group is circled on the structural formula above. Classify this group as primary, secondary, or tertiary.

Primary (1 mark)

(d) Ethanol can be produced from fermentation of glucose.

(i) Write a balanced equation for the hydrolysis of disaccharides to glucose.

C12H22O11 + H2O 2C6H12O6

1 mark for balanced equation1 mark for formula (2 marks)

(ii) State one condition needed for fermentation of glucose.

Any two Optimum T between 20°C to 30°C Oxygen must be almost totally excluded from fermentation vessel

(1 mark)

Total: 20 marks