[uks] Chemistry 2005(mock) Paper1(e)

2005-F.5 MOCK EXAM-CHEM 1-2

-1-

SECTION A Answer ALL questions in this Section. Write your answers in the spaces provided. 1.

The incomplete diagram below represents the arrangement of the ions in crystals of sodium chloride.

sodium ion

(a) elec

(i)

Complete the diagram by adding the missing ions.

(ii)

How does this crystal structure explain the fact that sodium chloride cannot conduct an electric current when in the solid state?

p

(iii) The melting point of sodium chloride is 801 oC. Explain why it has such a high melting point.

(b)

Give an industrial use of sodium chloride.

(5 marks)

2005-F.5 MOCK EXAM-CHEM 1-3

-2-

Go on to the next page

Please do not write in the margin

chloride ion

2.

ChemKong

Painting helps to prevent this.

(a)

Why is corrosion faster in sea water than in fresh water?

(b)

Why does painting help to prevent rusting?

(c)

Describe another way in which the ship could be protected from rusting.

(d) Steel is an alloy of iron. Iron is extracted from iron(III) oxide. equatequation, how iron is extracted from iron(III) oxide.

Explain your answer.

Describe, with appropriate

(7 marks)

2005-F.5 MOCK EXAM-CHEM 1-4

-3-

Please do not write in the margin

Steel ships can suffer from rusting.

3.

For each of the following experiments, state an expected observation and write a chemical equation for the reaction involved. (a)

Bubbling sulphur dioxide into acidified potassium dichromate solution.

(b)

Putting a small piece of calcium into water.

4.

A student carried out an experiment on thermal decomposition of limestone. (a)

Write an equation for thermal decomposition of limestone.

(b)

A gas is evolved in thermal decomposition of limestone.

t

(i)

Draw an experimental set-up to identify the gas.

(ii)

State any observable change for the test. test.

The gas can be tested with lime water.

Write an equation to explain the change in the

(5 marks) 2005-F.5 MOCK EXAM-CHEM 1-5

-4-

Go on to the next page

Please do not write in the margin

(4 marks)

5.

Petrol vapour is mixed with air before being burned in a car engine. The amount of petrol in the mixture can be varied. The amounts of polluted gases, nitrogen dioxide and carbon monoxide, in the exhaust emissions from cars depend on the mixture used, as shown in the graph below. carbon monoxide

concentration of pollutant gases

nitrogen oxide

(a) m

Describe how the concentration of carbon monoxide varies as the percentage of petrol in the mixture increases. Explain the change.

(b) h

The car engine releases most energy when there is 7.2 % petrol in the mixture. Suggest why the highest concentration of nitrogen oxide is produced in the engine under the conditions.

(c)

Suggest how carbon monoxide and nitrogen oxides are removed from car exhausts.

(5 marks) 2005-F.5 MOCK EXAM-CHEM 1-6

-5-

Please do not write in the margin

percentage of petrol in air/ petrol mixture

The diagram represents the structure of a common plastic.

(a)

Draw the structure of the monomer from which it is made.

(b)

Disposal of this plastic by landfilling will cause environmental problems.

(c)

The plastic can be used to manufacture plastic pipes.

Explain.

(i)

How could a length of straight pipe be bent to fit the desired curvature in a particular drainage system? Explain your answer.

(ii)

Used plastic pipes are usually destroyed by burning in incinerators.

drain

Explain why the incineration of the plastic may cause environmental problem.

(5 marks) 2005-F.5 MOCK EXAM-CHEM 1-7

-6-

Go on to the next page

Please do not write in the margin

6.

7.

Usage: For white cotton Usage: Machine Machine Wash: Wash: To every 30 litres water add 1/2 cup of the bleach Hand Wash: To every 5 litres add 2/3 Hand Wash: capful ..........

(a)

(i)

Name the gas given off.

(ii)

Write an equation for the formation of the gas.

(b) On the next day, he came back to the laboratory and found that the coloured papers near the turned wh beaker turned white. Explain briefly with the help of equations.

(c) fo

Mr. Kwok, the supervisor of Mr. Kong, investigated this event and gave him several suggestions for improvement. One was that Mr. Kong should put a warning statement on the bottle. Write the warning statement that should be displayed on the bottle of bleach.

(7 marks) 2005-F.5 MOCK EXAM-CHEM 1-8

-7-

Please do not write in the margin

In an experiment to determine the bleaching power of a bottle of bleach, Mr. Kong poured 150 cm3 of the bleach to a conical flask and then added dilute hydrochloric acid to the solution. Unexpected large amount of pale green gas was given off. He left the laboratory immediately.

8.

Consider the following flow chart. glucose

Process 1

Process 2

ethanol

ethanoic acid

Condensation compound X

Name process 1.

(b) i

Draw a diagram to show how the oxidation of ethanol to ethanoic acid in process 2 is carried out in the laboratory.

Please do not write in the margin

(a)

(c) Write the chemical equation for the condensation reaction between ethanol and ethanoic acid. Nam Name one addit ional reagent required for this reaction.

(d)

Give the IUPAC name for the product formed by the condensation reaction.

(7 marks) 2005-F.5 MOCK EXAM-CHEM 1-9

-8-

Go on to the next page

For question 9, candidates are required give a paragraph-length answer. In this question, 6 marks will be awarded for chemical knowledge and 3 marks for effective communication. 9.

Concentrated sulphuric acid shows different chemical properties when compared with dilute sulphuric acid. Discuss the differences in their chemical properties and illustrate your answer with appropriate examples and equations.

Please do not write in the margin

(9 marks)

2005-F.5 MOCK EXAM-CHEM 1-10

-9-

Please do not write in the margin

END OF SECTION A

2005-F.5 MOCK EXAM-CHEM 1-11

-10-

Go on to the next page

SECTION B Answer ALL questions in this Section. Write your answers in the spaces provided. 10. Consider the following experimental set-up.

zinc electrode

silver electrode

carbon electrode X

carbon electrode Y

silver nitrate solution

Dilute sulphuric acid set-up I

(b)

Set-up I acts as an electrochemical cell in the above set-up. (i)

Deduce the direction of electrons flow.

(ii)

Explain why set-up I is not a reliable source of electricity.

(i)

What would be observed at electrode X after the circuit is closed?

(ii)

Write half-equations for the reactions occurred at electrodes X and Y respectively.

(iii) Explain, in terms of preferential discharge of ions, how the product is formed at electrode Y. (c)

Describe the change on the solution in set-up II, after the circuit has been closed for 1 hour? (8 marks)

2005-F.5 MOCK EXAM-CHEM 1-12

-11-

Please do not write in the margin

(a)

set-up II

Please do not write in the margin

2005-F.5 MOCK EXAM-CHEM 1-13

-12-

Go on to the next page

11. 0.6 g of zinc was added to 10 cm3 of 0.5 mol dm-3 hydrochloric acid, using the apparatus below.

0.6 g zinc

The graph below shows how the volume of the gas collected during the reaction.

(a) (b) terature (c)

Write an equation for the reaction occurred. Calculate the maximum volume of gas which could be collected in the gas syringe at room temperature and pressure. Describe and explain the change in the rate of reaction as the reaction progresses.

(d)

The experiment was repeated using dilute sulphuric acid of the same concentration. Suggest how the rate of reaction would differ from the reaction between zinc and hydrochlorhydrochloric acid. Explain your reasoning. (Molar volume of gas in room temperature and pressure = 24.0 dm3) (10 marks)

2005-F.5 MOCK EXAM-CHEM 1-14

-13-

Please do not write in the margin

Volume of gas

Please do not write in the margin

2005-F.5 MOCK EXAM-CHEM 1-15

-14-

Go on to the next page

12. A student carried out the following experiment to prepare copper(II) sulphate crystals, CuSO4·5H2O. 100 cm3 of 2 M sulphuric acid was first diluted to 250.0 cm3 with distilled water. Excess copper(II) carbonate was added to 50 cm3 of the diluted acid in a beaker. After the reaction, the mixture was filtered and the filtrate was warmed until a saturated solution was obtained. The solution was allowed to cool. After a day, the crystals formed were filtered off, washed and dried. (a)

Write the chemical equation for the reaction between copper(II) carbonate and sulphuric acid.

(b) How could the student know that the reaction between copper(II) carbonate and the diluted acid was was complete? (c) What is meant by the term ‘saturated solution’? solllllsolution to see whether the solution is saturated.

Suggest a test on the copper(II) sulphate

(d)

Why do copper(II) sulphate crystals lose mass when they are heated?

(e)

Calculate the theoretical mass of copper(II) sulphate crystals formed.

Please do not write in the margin

(9 marks)

2005-F.5 MOCK EXAM-CHEM 1-16

-15-

Please do not write in the margin

2005-F.5 MOCK EXAM-CHEM 1-17

-16-

Go on to the next page

For question 13, candidates are required give a paragraph-length answer. In this question, 6 marks will be awarded for chemical knowledge and 3 marks for effective communication. 13. Describe briefly how soap can be produced from vegetable oil in the laboratory. State the problems associated with the use of soap.

Please do not write in the margin

(9 marks)

2005-F.5 MOCK EXAM-CHEM 1-18

-17-

Please do not write in the margin

END OF PAPER

2005-F.5 MOCK EXAM-CHEM 1-19

-18-