1993 Paper 2

1993 Hong Kong Certificate Of Education Examination Chemistry Paper II There are 50 questions in the paper. 1.

A. Ag + 2H+ → Ag+ + NO2 + H2O B. Ag + 4H+ + 2NO3– → Ag + 4NO2 + O2 +

Which of the following pairs of atoms/ions has the same number of electrons?

C. D.

A. Mg2+ and F B. Cl and Ne C. K + and O2D. Cl- and S22.

The element, sodium to chlorine, in the third period of the Periodic Table show a gradual change in properties. Which of the following changes is correct? A. B. C. D.

3.

Their melting points increase. Their ability to gain electrons increases. Their oxides change from acidic to basic. Their chlorides change from covalent to ionic.

6.

Which is the percentage by mass of silver in the coin? (Relative atomic masses: Cl = 35.5, Ag = 108) A. B. C. D.

45 60 75 90

7. CO2(g) + CaCO3(x) + H2O(y)→Ca(HCO3)(z) In the above chemical equations, which of the following combinations is correct?

Which of the following molecules is linear in shape? A. B. C. D.

2H2O 3Ag + 4HNO3 → AgNO3 + 3NO2 + 2H2O Ag + 4HNO3 → AgNO3 + 3NO2 + 2H2O

A. B. C. D.

tetrachloromethane water ammonia carbon dioxide

x aq s s s

y l aq l l

z aq s s aq

8. The molecular formula of gaseous element X is 4.

The element with atomic number 11 will combine most readily with the element whose atomic number is

X2. If the relative atomic mass of X is 19, what is the number of molecules in 114g of the gas? (Avogadro’s number = 6.02 x 1023)

A. B. C. D.

A. 3 B. 6 C. 3 x 6.02 x 1023 D. 6 x 6.02 x 1023

12 13 17 18

Direction: Q.5 and Q.6 refer to the following experiment: A silver coin, with a mass of 12.00g, was dissolved completely in concentrated nitric acid. When excess potassium chloride solution was added to the resulting solution, 14.35g of a white precipitate were obtained. 5.

Which of the following equations correctly represents the reaction between silver and concentrated nitric acid?

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9. 0.21g of a gaseous hydrocarbon occupies 0.12dm3 at room temperature and pressure. If this hydrocarbon has the empirical formula CH2, what is its molecular formula? (Relative atomic mass : H = 1.0, C = 12.0; Molar volume of gas at room temperature and pressure = 24.0dm3)

A. B. C. D.

C2H4 C3H6 C4H8 C5H10

10. (This item was deleted in the live paper as it was found to be unsuitable.)

metals? A. B. C. D.

Which of the following compound does NOT give a characteristic colour to the flame in the flame test? A. B. C. D.

potassium chloride calcium chloride copper(II) chloride magnesium chloride

15. The oxidation number of copper remains unchanged when A. magnesium ribbon is added to copper(II) sulphate solution. B. sodium carbonate solution is added to copper(II) nitrate solution. C. carbon is heated with copper(II) oxide. D. copper foil is burnt in chlorine.

11. The following substances were burnt in oxygen and the products were mixed with water. Which of these substances would produce a resulting solution with the highest pH value? A. B. C. D.

W>X>Y W>Y>X X>Y>W Y>W>X

calcium iron sulphur carbon

16. In which of the following equations does the underlined substance undergo reduction?

A. B. C. D.

12. A mixture contains copper powder and zinc powder. In order to remove the zinc powder, the mixture is heated with an acid and filtered. Which of the following acids should be used?

2H2O + 2K → 2KOH + H2 Fe2(SO4)3 + 2KI → 2FeSO4 + K2SO4 + I2 2H2S + SO2 → 3S + 2H2O NaClO + SO2 + H2O → NaCl + H2SO4

17. A. B. C. D.

dilute nitric acid concentrated nitric acid dilute sulphuric acid concentrated sulphuric acid

13. 0.12g of sodium metal is added to a large volume of water. When the reaction is completed, the resulting solution is treated with 0.2M hydrochloric acid. What is the volume of the acid required, to the nearest cm3, for complete neutralization? A. B. C. D.

13 26 39 52

With reference to the above diagram, which of the following statements is correct?

14. The carbonates of three metals W, X and Y are separately heated strongly and the results obtained are tabulated below: Metal W X Y

Action of heat on metal carbonate CO2(g) and O2(g) evolved No reaction CO2(g) evolved

Which of the following arrangements represents the correct decreasing order of reactivity of the

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A. The electrode made of metal X is the positive pole. B. Copper is at a higher position in the electrochemical series than metal X. C. The mass of the copper electrode decreases. D. The mass of the electrode made to metal X decreases. 18. In an electrolysis experiment, a steady current of 0.5A was passed through an aqueous solution of the chloride of an unknown metal M for 1 hour 20 minutes. At the end of the experiment,

1.15g of metal M were deposited at the cathode. What is the formula of the chloride? (Relative atomic mass of metal M = 140; 1 faraday = 96500 coulombs)

21. In Dish II, which of the following colours will develop around the iron wire and the copper wire? iron wire copper wire A. pink blue B. blue pink C. pink no colour D. blue no colour 22. Which of the following reactions would product a halogen?

A. MCl B. MCl2 C. MCl3 D. MCl4 19.

(1) sodium chloride + concentrated sulphuric acid (2) sodium bromide + concentrated sulphuric acid (3) sodium iodide + concentrated sulphuric acid

In the above experiment, which of the following major products will be liberated at the electrodes? cathode magnesium magnesium hydrogen hydrogen

A. B. C. D.

anode oxygen bromine bromine oxygen

Directions: Q.20 and Q.21 refer to the following experiment: Three different pairs of metal wires are placed separately in petri dishes (as shown in the diagram below) containing a mixture of gelatin, potassium hexacyanoferrate(III) solution and phenolphthalein solution. 20.

A. B. C. D.

(1) only (3) only (1) and (2) only (2) and (3) only

23. Which of the following statements about a solution of hydrogen chlorides in water is correct? A. The hydrogen chloride exists as molecules in the solution. B. The hydrogen chloride is slightly ionized in water. C. The pH value of the solution is greater than 7. D. The reaction between the solution and aqueous ammonia is exothermic. 24. There is a gradual change in the properties of halogens from chlorine to iodine. Which of the following properties are in the order. chlorine < bromine < iodine?

Which of the following statements are correct? (1) The iron wire in Dish I does not corrode readily. (2) The iron wire in Dish II corrodes readily. (3) The iron wires in Dish III do not corrode. A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

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(1) oxidizing power (2) density (3) boiling point A. B. C. D.

(1) and (2) only (2) and (3) only (1) and (3) only (1), (2) and (3)

25. Which of the following properties apply to sulphur dioxide? (1) It bleaches dry litmus paper. (2) It decolorizes bromine water. (3) It supports the burning of magnesium ribbon.

A. B. C. D.

transferred to flask Y and heated as shown below:

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

30. What is the function of the piece of apparatus labeled X?

26. On heating, blue copper(II) sulphate crystals gradually change to a white powder. Which of the following statements are correct? (1) Heat would be liberated if water is added to the white powder. (2) On further heating, the white powder would turn reddish-brown. (3) A chemical change occurs during the heating of the blue crystals. A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

27. Which of the following solutions forms a precipitate with excess aqueous ammonia? A. B. C. D.

copper(II) chloride solution aluminum nitrate solution zinc sulphate solution sodium chloride solution

28. In the above experiment, the gaseous products are

A. nitrogen and water vapour. B. nitrogen and hydrogen. C. nitrogen monoxide and water vapour. D. nitrogen monoxide and hydrogen. 29. In the above process, which of the following combinations is correct?

A. B. C. D.

Process fractional distillation fractional distillation cracking cracking

X an alkane an alkene an alkane an alkene

Direction: Q.30 and Q.31 refer to the following experiment: A mixture of methyl propanoate and sulphuric acid was allowed to react by heating under reflux for some time until equilibrium was reached. The resulting mixture M was then

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A. to condense the products in M B. to separate the products in M C. to prevent the loss of the products in M due to evaporation D. to prevent the loss of the reactants in M due to evaporation 31. The first fraction of the distillate collected in flask Z is mainly A. B. C. D.

methanol propan-1-ol methanoic acid propanoic acid

32. Which of the following substances can react with propene? (1) concentrated sodium hydroxide solution (2) acidified potassium permanganate solution (3) ethanol A. B. C. D.

(1) only (2) only (1) and (3) only (2) and (3) only

33. Which of the following statements about fossil fuels is correct? A. They are liquids or gases. B. They are all formed from plants which died millions of years ago.

C. They can be recycled to help conserve energy resources. D. They cause air pollution when burnt.

34. Which concentrated sulphuric acid is added dropwise to a solution containing urea and methanal in a test tube with shaking, a white solid can be formed. Which of the following statements about this experiment is/ are correct? (1) The reaction involved is condensation polymerization. (2) Concentration sulphuric acid acts as an oxidizing agent. (3) The white solid is a thermoplastic substance. A. B. C. D.

(1) only (2) only (1) and (3) only (2) and (3) only

35. A polymer has the following structure:

38. The reaction between X(aq) and Y(aq) is represented by the following equation: X(aq) + Y(aq) ↔ Z(aq) Which of the following graphs represents the change of concentration of Y(aq) with time when fixed quantities of X(aq) and Y(aq) are introduced into a closed container?

Its monomer is A. B. C. D.

chloroethene 1,1-dichloroethane 1,2-dichloroethane 1,2-dichloroethane

36. Consider the following equilibrium system: Which of the following statements about the above system is/are correct? (1) When the temperature is increased, the colour of the system becomes darker. (2) When the pressure is increased, the total number of molecules in the system increases. (3) When the volume is increased, the colour of the system becomes darker immediately. A. B. C. D.

(1) only (2) only (1) and (3) only (2) and (3) only

37. A mixture of ammonia and oxygen is passed over red hot platinum for a few minutes. Which of the following graphs represents a plot of the mass of platinum against time?

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Direction: Q.39 and Q.40 refer to the following experiment on the study of the rate of reaction between hydrochloric acid and sodium thiosulphate solution: 10 cm3 portions of 2.0M hydrochloric acid were added to four separate conical flasks each containing sodium thiosulphate solution which was prepared respectively as follows: conical flask W X Y

sodium thiosulphate solution concentration volume 1.0M 80 cm3 1.5M 60 cm3 2.5M 30 cm3

volume of water 10 cm3 30 cm3 60 cm3

Z 3.0M 20 cm3 70 cm3 39. In which of the above conical flasks does the reaction proceed at the fastest rate? A. B. C. D.

W X Y Z

A. B. C. D.

44. Which of the following statements is INCORRECT?

40. Which of the following apparatus should be used when carrying our the above experiment in addition to the conical flasks?

A. Tin is used for making food cans. B. Sulphuric acid is used for making soap. C. Ammonium chloride is used for making dry cells. D. Chlorine is used for sterilizing drinking water.

(1) syringe (2) stop watch (3) measuring cylinder A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

41. Which of the following experiments is potentially hazardous and should NOT be carried out on a laboratory bench?

Direction: Each question below (Question Nos. 45 to 50) consists of two separate statements. Decide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from A to D according to the following table: 1st statement Concentrated sulphuric acid can be used to prepare nitric acid.

2nd statement Sulphuric acid is more volatile than nitric acid

46.

Sodium carbonate is not decomposed by heat.

Sodium carbonate is an ionic compound.

47.

A flash of lightning causes nitrogen monoxide to be formed in the air.

Lightning provides sufficient energy for nitrogen to react with oxygen in the air.

48.

Which car exhaust gases are bubbled into citrated blood, the colour of the blood gradually becomes cherry red.

Nitrogen dioxide is present in car exhaust gases.

49.

100cm3 of 1M hydrochloric acid react with excess magnesium ribbon at the same rate as 100cm3 of 1M sulphuric acid.

Both acids contain the same concentration of H+(aq) ions.

50.

When a reversible reaction is at equilibrium, the amount of product increases on addition of a catalyst.

A catalyst can increase the rate of the forward reaction.

45. A. heating ammonium nitrate strongly in a test tube. B. passing ethane through bromine water in a conical flask C. adding a small piece of sodium to a beaker of ethanol D. pouring a small amount of concentrated nitric acid into a trough of water

42. Which of the following solids can be purified using the above set-up? A. B. C. D.

potassium iodide ammonium chloride lead(II) bromide sodium hydrogencarbonate

43. Which of the following reagents can be used to distinguish between aluminum sulphate solution and lead(II) ethanoate solution?

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barium chloride solution sodium hydroxide solution nitric acid hydrochloric acid

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