Pok Oi Hospital Tang Pui King Memorial College

Second Term Examination ( 1996-1997 )

F.4    Chemistry I

Class                :           ________________                Date   :   ________________

Name               :           ________________                Time allowed : 90 mins

Class Number  :      ________________                       ( P.1 - P.4 /38 )

Instructions to students:

 1. The total score of this paper is 90 marks.

2. There are two sections in this paper.

3. Answer all questions.

4. Answer Section A and Section B in the answer book provided.

Section A  (36 marks)

1. Tuning knobs on electrical appliances are often made of plastics plated with metal

    coatings.

     (a) What is the purpose of plating the knobs with metals?

     (b) Before being electroplated with nickel, plastic tuning knobs are first coated with

         copper. Explain why.

     (c) Draw a labeled diagram to show the apparatus you would use to electroplate the

         copper-coated plastic knobs in a laboratory.

         Include in your diagram: a battery, an ammeter, a rheostat, a named anode, a

         named cathode and a named electrolyte.

(6 marks)

2. (a) Suggest a danger in perming hair too often.

     (b) You want to remove the waves from your hair. Suggest a solution you can use.

         Explain your choice.

     (c) After washing hair with shampoo, many people use hair conditioners

(I)                 From the results of your experiments, are hair conditioners acidic or

alkaline?

         (II)   Suggest a reason for the pH values of the hair conditioners.

(5 marks)

3. Universal indicator is a mixture of dyes. The pH of the indicator ranges from 0 to 14.

    To test the pH of a solution, one can simply add to it several drops of indicator.

 (a)    What conclusions can you draw if the colour of the solution is green after

several drops of indicator is added to it?

       (b)   What colour will be shown if the indicator is added to 5 cm³ of sodium

hydroxide solution? What does the test show?

          (c) Name other three acid-base indicators.

(7 marks)

4. (a) A bottle of window cleaner contains an alkali. What is the name of the alkali?

     (b) What does the glass cleaner feel like?

     (c) Suggest ONE precaution when you handle the glass-cleaner in home.

       Explain briefly.

(4 marks)

5. The following questions refer to the reaction below:

                             MnO₄^- (aq) + I ^- (aq) ® Mn²⁺(aq) + I₂ (aq)

     (a) State which is the oxidizing agent in this reaction.

     (b) Write half equations for the oxidation reaction and reduction reaction.

     (c) Write a balanced equation for the above reaction.

     (d) What can be observed in this reaction?

(5 marks)

6. Discuss the industrial importance of electrolysis with reference to THREE uses of

    electrolysis. (Diagrams and equations are NOT required.)

(9 marks)

( 3 of the 9 marks for this question will be awarded for the effective communication of

knowledge in Chemistry. )

 Section B  (54 marks)

7. The diagram below shows an experimental set-up for the electrolysis of molten

    lead(II) bromide and dilute sulphuric acid in series.

    (a) (I)    Classify the electrodes P, Q, R and S as cathode or anode.

       (II)   Solid lead(II) bromide cannot be used to replaced molten lead(II)

bromide in the electrolysis. Explain why.

(6 marks)

(b) (I) What would be observed around electrode P after some time? Write an  

ionic equation for the reaction.

  (II)   What would be observed around electrode Q after some time? Write an

      ionic equation for the reaction.

             (III)  At which electrode does reduction occur, electrode P or electrode Q?

(5 marks)

    (c) A colourless gas X was given off around the electrode R.

         (I)    What is gas X?

         (II)   Explain the formation of gas X around electrode R using preferential

              discharge. Give the appropriate ionic equation.

(4 marks)

    (d) A colourless gas Y was given off around the electrode S.

         (I)    Suggest the name of gas Y.

         (II)   Write an equation for the formation of gas Y.

         (III)  Suggest a chemical test for gas Y.

(3 marks)

8. (a) Consider the following hazard warning symbols:

Choose TWO labels which should be displaced on a bottle of concentrated nitric acid. Explain your choice.

(3 marks)

    (b) Why should concentrated nitric acid be stored in dark bottles?

(1 mark)

    (c) What would be observed when a piece of copper is added to

         (I)    concentrated nitric acid, and

         (II)   dilute nitric acid?

         Explain with the aid of chemical equations.

(6 marks)

    (d) How would you dilute 5M nitric acid to 1M nitric acid? Describe the procedure

         briefly.

(3 marks)

    (e) Sulphuric acid can react with each of the following:

         (I)    copper(II) sulphate crystals

         (II)   sugar

         (III)  magnesium

In each case, state whether concentrated or dilute sulphuric acid is used. Describe

       what would be observed and state the role of sulphuric acid.

(6 marks)

    (f) How would you prepare dilute sulphuric acid from concentrated sulphuric acid?

(2 marks)

9. (a) Calculate the number of particles of the following substances.

          (I)    number of atoms in 9g water

         (II)   number of molecules in 32g surphur dioxide

         (III)  number of ions in 11.1g calcium chloride

     ( relative atomic mass: H = 1; O = 16; Cl = 35.5; S = 32; Ca = 40;

     Avogadro’s number = 6.02x10²³)

(9 marks)

    (b) Calculate the concentration of the following solutions.

         (I)    250 cm³ solution containing 10g sodium hydroxide

         (II)   200 cm³ water added to 100 cm³ 2M sulphuric acid

           (III)              11.7g sodium chloride added to 100 cm³ 0.5M sodium chloride

solution.

     ( relative atomic mass: H = 1; O = 16; Na = 23; S = 32; Cl = 35.5)

(6 marks)

END OF PAPER

Pok Oi Hospital Tang Pui King Memorial College

Second Term Examination ( 1996-1997 )

F.4    Chemistry II

Class                :           ________________                Date     :          __________________

Name               :           ________________                Time allowed :  60 mins

Class Number :            ________________                ( P.1 - P.12 /38 )

Instructions to students:

 1. The total score of this paper is 60 marks.

2. Answer all questions.

1. Which of the following pairs of particles are identical ?

  (I) Hydrogen molecule and hydrogen ion.

  (II) Proton and neutron

  (III) Hydrogen ion and proton

  (IV) Iron (II) ion and Iron (III) ion.

  A. (I)

  B. (II)

  C. (III)

  D. (IV)

Directions : Questions 2-4 refer to the following diagrams.

2. Which of the diagram is a correct representation of a mixture of pure elements.

  A. I

  B. II

  C. III

  D. IV

3. Which of the diagram is a correct representation of steam

  A. I

  B. II

  C. III

  D. IV

4. Which of the diagram shows a monoatomic gas.

  A. I

  B. II

  C. III

  D. IV

5. What characteristic do mercury and bromine have in common?

  A. They are both brown in colour.

  B. They both conduct electricity.

  C. They are the only liquid elements.

  D. They are the only liquid metals.

6. Potassium has 2 major isotopes. They are ³⁹K and ⁴¹K. If the relative atomic mass of

  naturally occurred potassium is 39.14. What is their relative abundance?

                ³⁹K               ⁴¹K   

  A.            7%               93%

  B.           93%                7%

  C.           25%               75%

  D.           75%               25%

7. In the modern Periodic Table, the elements are arranged in order of

  A. atomic mass.

  B. mass number.

  C. atomic number.

  D. the number of neutrons in the nucleus.

8. In moving across a period of the Periodic Table from Group I to Group VII,

  A. the elements change from metal to semi-metal.

  B. the atomic mass of the elements increases.

  C. the elements show similar chemical properties.

  D. the number of electron shells in the elements increases gradually.

9. In the modern Periodic Table, the areas A, B and C represent

   A. metals, noble gases and non-metals respectively.

  B. semi-metals, metals and non-metals respectively.

  C. metals, semi-metals and halogens respectively.

  D. non-metals, halogens and noble gases respectively.

10. Which species contains the least number of electron?

   A. O^2-

   B. F

   C . Na

   D. Al³⁺

11. Strontium is a group II element in the 5th period. Which of the following represents

   possible electronic configuration for strontium?

   A. 2,8,8,8,8,4

   B. 2,8,18,8,2

   C. 2,8,18,10

   D. 2,8,10,8,8,2

12. Lithium is a group I element in the periodic table, which one of the followings about

   its properties is INCORRECT?

   A. It is soft enough to be cut with a knife.

   B. It forms an alkaline solution when it is put into a beaker of water.

   C. It is shiny metal.

   D. When it is put into water, lithium catches fire immediately.

13. A natural occurring substance Y has the following structure.

 Which of the following statement is/are TRUE.

   (I) Y is very hard

   (II) Y is a covalent compound

   (III) Y is carbon

   A. (I) only

   B. (II) and (III) only

   C. (I) and (II) only

   D. (I) and (III) only

14. What is formed when an element X of atomic number 19 reacts with an element Y

   of atomic number 17?

   A. A covalent compound of formula XY

   B. A covalent compound of formula XY₂

   C. An ionic compound of formula XY

   D. An ionic compound of formula X₂Y

15. The following apparatus is set up to test the conductivity of molten lead(II) bromide.

   Why is heating of the lead(II) bromide necessary?

   A. To provide energy for solid lead(II) bromide to react

   B. To remove impurities in the lead(II) bromide.

   C. To allow the ions of lead(II) bromide free to move.

   D. To increase the viscosity of the molten lead(II) bromide.

16. Which of the following is/are electrolyte(s)?

   (I) Copper(II) chloride

   (II) Sulphur

   (III) Diamond

   A. (I) only

   B. (I) and (II)

   C. (II) and (III)

   D. (I), (II) and (III)

Directions : Questions 17-18 refer to the following table which provide some properties

          of four chlorides.

17. Which of the chlorides is /are compounds of simple molecular structure?

   A. W only

   B. X only

   C. X and Y only

   D. X and Z only

18. Which of the chlorides conduct(s) electricity at 710 ^oC?

   A. W only

   B. X only

   C. X and Y only

   D. W, Y and Z only

19. Which of the following compounds has the largest number of lone pairs of electrons

   on the central atom?

   A. CCl₄

   B. NH₃

   C. CO₂

   D. H₂O

20. Helium has been used to replace hydrogen in filling up balloon. The main reason is

   A. Helium is cheaper than hydrogen.

   B. Helium molecule is smaller than hydrogen molecule therefore helium is lighter.

   C. Helium is chemically inert.

   D. Helium is less toxic than hydrogen.

21. At room temperature CO₂ is a gas but SiO₂ is a solid. The reason is that

   A. CO₂ is a covalent compound whereas SiO₂ is an ionic compound.

   B. silicon is larger than carbon so that there are larger intermolecular forces existing

     between SiO₂ molecules.

   C. the density of SiO₂ is higher than that of CO₂.

   D. CO₂ exists as discrete molecules whereas SiO₂ exists as a giant network.

22. The price of a metal depends on

   (I) the cost of extraction of the metal.

   (II) the abundance of the metal.

   (III) the physical properties of the metal.

   A. (I) and (II)

   B. (I) and (III)

   C. (II) and (III)

   D. (I), (II) and (III)

23. Sodium is a good conductor of electricity but it is not used to make electrical wires

   because

    (I) it is too soft.

   (II) it is ductile.

   (III) it reacts with water and air.

   A. (I) only

   B. (I) and (II)

   C. (I) and (III)

   D. (II) and (III)

24. Magnesium has a higher melting point than sodium because

    A. magnesium is heavier than sodium.

   B. the atom of magnesium is larger than that of sodium.

   C. the metallic bonds between the atoms of magnesium are stronger than that in

     sodium.

   D. the arrangement of atoms in magnesium is more regular than that in sodium.

25. Which of the statements below is/are true about alloys?

   (I) An alloy is a mixture of a metal and other compounds.

   (II) An alloy has a different structure and properties from the pure metal.

   (III) The atoms in an alloy are of different size.

   A. (I) only

   B. (I) and (II)

   C. (II) and (III)

   D. (I), (II) and (III)

26. Which is the correct colour of rust indicator for the ion?

            Ion            Colour of Rust Indicator     

   A.       Fe²⁺                 yellow

   B.       Fe²⁺                 blue

   C.       Fe³⁺                 yellow

   D.       Fe³⁺                 blue

27. What are the necessary conditions for rusting?

   (I) Presence of water

   (II) Presence of air

   (III) Presence of electrolyte

   A. (I) and (II) only

   B. (I) and (III) only

   C. (II) and (III) only

   D. (I), (II) and (III)

28. In which case will the iron nail rust the fastest?

29. Which method can be used on a bicycle chain for the prevention of rusting?

   A. Coating with a layer of paint

   B. Coating with a layer of oil

   C. Galvanizing

   D. Tin plating

30. What is the most important reason for anodizing aluminium?

   A.To thicken the oxide layer

   B. To add colour to the aluminium

   C. To make the aluminium more attractive

   D. To increase the hardness

31. CO(w)+CuO(x)→Cu(y)+CO₂(z)

   The states are, respectively

       w          x           y           z     

   A.  s           s            s           g.

   B.  l           s            s            s.

   C.  g           s            s           g.

   D.  g           g            g           g.

32. wNH₃ (g) +xO₂ (g) →yNO (g) +zH₂O (l)

   The coefficients are, respectively

        w          x            y             z     

   A.   1           2            1              2.

   B.   1           3            1              5.

   C.   2           3            2              4.

   D.   4           5            4              6.

33. The followings are properties of metals X, Y and Z.

   (I) Only Y and Z react with dilute hydrochloric acid.

   (II) When Z is put into Y(NO₃)₂(aq) solution no visible reaction occur.

   The order of decreasing reactivity of the 3 metals is

   A. Z>Y>X

   B. Y>Z>X

   C. X>Y>Z

   D.Y>X>Z

34. Which metal is least affected chemically when heated in air?

 A. Silver

 B. Aluminium

 C. Zinc

 D. Magnesium

35. A metal oxide grows orange when heated and stays yellow when cooled. The metal is

 A. zinc.

 B. aluminium.

 C. lead.

 D. calcium.

36. Magnesium reacts with both water and dilute hydrochloric acid. Which statement(s)

   is /are CORRECT?

   (I) It reacts faster with water

   (II) It reacts faster with dilute hydrochloric acid.

   (III) Both reactions give hydrogen gas.

   A. (I) only

   B. (II) only

   C. (I) and (III)

   D. (II) and (III)

37. Which cell produces the largest voltage?

Directions: Questions 38 - 39 refer to the following lemon cell.

38. Which statement is INCORRECT?

 A.The zinc rod acts as the anode.

 B. The light bulb will not light if the copper rod is replaced by an aluminium rod.

 C. The electrolytes are the organic acid and mineral salts in the lemon.

 D. The light bulb will also light if the lemon is replaced by an orange.

39. The copper and zinc rods have to be cleaned with sandpaper before the experiment in

   order to

   A. remove the oxide and impurities.

   B. improve the reactivity of zinc.

   C. improve the reactivity of copper.

   D. prevent the formation of oxide on the rods.

Directions: Questions 40 - 41 refer to the following chemical cell.

40. Which statement concerning the cell is CORRECT?

   A. The platinum electrode in half cell X is the anode.

   B. Iron(II) is reduced at half cell Y.

   C. The sulphuric acid in half cell X is a catalyst.

   D. Electrons flow from Y to X via the external circuit.

41. Which observation is INCORRECT as current is produced?

   A. The cell voltage gradually decreases.

   B. The solution in X becomes colourless.

   C. The solution in Y becomes yellow.

   D. The mass of the platinum electrodes does not change.

42. Which cell supplies a voltage of less than 1.5V?

   A. Zinc-carbon cell

   B. Alkaline manganese cell

   C. Silver oxide cell

   D. Nickel-cadmium cell

43. Which is NOT contained in a zinc-carbon dry cell?

   A. Carbon rod

   B. Zinc cup

   C. Ammonium chloride

   D. Magnesium oxide

44. The function(s) of manganese(IV) oxide in a zinc-carbon dry cell is/ are

   (I) to prevent formation of hydrogen gas.

   (II) to act as a conductor.

   (III) to act as a reducing agent.

   A. (I) only

   B. (III) only

   C. (I) and (III) only

   D. (II) and (III) only

Directions:  Each question below ( Questions 45 -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:

45. All noble gases are inert.                                   Their outermost electron shell all have

                                                                                  been filled up with 8 electrons.

46. An element X having an atomic                          Atom of metal always have one electron

       number 11 is a metal.                                          in the outermost shell.

47. Within halogens, chlorine is a                              For group VII elements, reactivity

      gas whereas iodine is solid.                                        decreases when moving down the group.

48. Isotopes of a given element have                         All atoms of an element contain the same

      the same relative atomic mass.                               number of electrons.

49. Nickel-cadmium cells are more                          Nickel-cadmium is rechargeable.

   environment friendly than zinc-

   carbon cell.

50. Sodium is a stronger reducing                           Sodium is more ready to loss its electrons

   agent than magnesium.                                           than magnesium.

END OF PAPER