Pok Oi Hospital Tang Pui King Memorial College

Pok Oi Hospital Tang Pui King Memorial College

First Term Examination ( 1996-1997 )

F.4 Chemistry

Class : ________________ Date : __________________

Name : ________________ Time allowed : 90 mins

Class Number. : ________________ ( P.1 - P.7/38 )

Instructions to students:

The total score of this paper is 100 marks.

There are two sections in this paper.

Answer all questions.

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

Section A (40%)

1. Which of the following properties is not a property of metals?

A. They are good conductors of heat and electricity.

B. They have high densities.

C. They usually have high melting points.

D. They do not react with air and water.

2. Which is the most abundant element in the earth’s crust?

A. Oxygen

B. Iron

C. Silicon

D. Aluminium

3. An atom has an atomic number of 20 and a mass number of 40. The nucleus of this

atom contains

Protons Neutrons

A. 10 10

B. 20 20

C. 20 40

D. 40 20

4. Which of the following statements is/ are correct?

(1) The nucleus of any element must contain proton(s) and neutron(s).

(2) In an atom, the number of protons must be equal to that of neutrons.

(3) The mass of one proton equals that of one neutron.

(4) The mass of one electron is only 1/ 1870 of that of neutron or proton.

A. (1) only

B. (2) only

C. (3) and (4) only

D. (1), (3) and (4) only

5. Which of the following sets of elements is/ are in the same group in the Periodic

Table?

(1) Calcium, iron, magnesium

(2) Lithium, sodium, potassium

(3) Oxygen, nitrogen, sulphur

(4) Fluorine, chlorine, iodine

A. (4) only

B. (1) and (3) only

C. (2) and (4) only

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

6. Which of the following statements about the Periodic Table is not correct?

A. Elements are arranged in an increasing order of the atomic number.

B. Elements having the same number of outermost shell electrons belong to the same

group.

C. Metals are placed on the right- hand side of the table.

D. Inert gases are Group 0 elements.

7. An element W has an electronic configuration of 2,8,2. Which of the following

statements about W are correct?

(1) It forms an ion of W^2+.

(2) It burns vigorously in air.

(3) The compound WCl₂ is ionic.

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

8. Which of the following statements is correct concerning X and Y?

A. They are isoelectronic.

B. Y is an anion which is formed by gaining two electrons.

C. They have the same number of protons.

D. They have the same size.

9. The electronic structure of the atoms X, Y and Z are given below.

X: 2,1 Y: 2,6 Z: 2,7

What are the formulae of the compounds formed between (I) X and Y, (II) X and Z?

X and Y X and Z

A. X₂Y XZ

B. XY₂ XZ

C. X₂Y X₂Z

D. XY XZ₂

Directions: Q.10 to 12 refer to the following set- up which is used to detect the migration

of coloured ions in an electric field.

10. Which of the following substances is best used to damp the filter paper?

A. Tap water

B. Sodium chloride solution

C. Oil

D. Distilled water

11. Which is the correct diagram for the result?

Solution used Observation

12. What would be observed if an a.c. supply is used instead of a d.c. supply?

A. The coloured spot moves to the other direction.

B. The coloured spot moves to the same direction.

C. The coloured spot does not move.

D. The coloured spot splits and moves to both directions.

13. The compound formed between an alkali metal an a halogen would

A. have a low melting point.

B. conduct electricity in the solid state.

C. conduct electricity when molten.

D. be insoluble in water.

14. Which of the following diagrams is the electronic diagram of calcium oxide?

15.Calcium oxide has a high melting point because

A. the electrostatic force between the ions is very strong.

B. the covalent bond between the atoms is very strong.

C. calcium is a reactive metal.

D. the ions are not mobile.

16. Which of the following statements is INCORRECT?

A. Sodium chloride is soluble in water because the ions are “pulled away” by the

polar water molecules.

B. Wax is soft because the molecules are held by weak covalent bonds.

C. Quartz is hard because it is a covalent giant structure.

D. Carbon dioxide has a low boiling point because the molecules are held by weak

Van der Waals’ forces.

17. A substance melts at -20^oC and boils at 70 ^oC. The substance

(1) is a liquid at room temperature.

(2) has a molecular structure.

(3) has Van der Waals’ forces between the molecules.

Which of the following is correct?

A. (1) and (2) only

B. (1) and (3) only

C. (2) and (3) only

D. (1), (2) and (3)

18. What is responsible for the electrical conductivity of metals?

A. The free- moving electrons

B. The positive ions

C. The close packing of atoms

D. The giant lattices

19.The metals found in bronze include:

A. tin and nickel.

B. tin and manganese.

C. copper and zinc.

D. copper and tin.

20. An alloy is generally stronger and harder because

A. the metal atoms cannot slide over each other easily.

B. different metal atoms strongly attract each other.

C. the elements in the alloy form a more stable compound.

D. a new type of bond is formed in the alloy.

End of Section A

Section B (60%)

1. A, B and C are three metal elements in the Period 3 of the Periodic Table. The

atomic numbers of A, B and C are 11, 12 and 13 respectively.

(a) State

(I) the group number of A;

(II) the electronic configuration of B;

(III) the charge on an ion of C.

(b) In what way are the electronic configurations of the atoms of elements A, B and C

(I) similar to one another?

(II) different from one another?

(II) Rubidium is another member of this family. Predict what would happen when

rubidium is added to dilute hydrochloric acid.

(7 marks )

2. The diagrams below show the structures of three solids A, B and C:

Structure of A Structure of B Structure of C

(a) Name THREE substances which have the same structures as A, B and C

respectively.

(b) Substance B cannot conduct electricity in solid state. However, it can conduct

electricity in molten state.

(I) Explain the electrical conductivity of substance B in solid state and molten state.

(II) Draw a labelled diagram to show the experimental set- up you would use to prove the electrical conductivity of substance B in molten state.

(II) Name another allotropic form of substance C.

(d) In terms of the forces between particles, explain why there is a large difference in

melting point between

(I) A and B.

(II) A and C.

In each case, state which of the two solids is expected to have the higher melting point.

( 14 marks )

3. (a) The following experimental set- up is used to investigate the rusting process under

different conditions.

(I) Which nail(s) in the above test tubes would rust after one day?

(II) What is the function of

(1) anhydrous calcium chloride in tube A.

(2) oil in tube B?

(III) (1) If car exhaust gas is used instead of air in tube C, will rusting occur?

(2) If your answer is positive in (1), will the nail rust faster in car exhaust gas than in the air? Explain your answer.

If your answer is negative, explain why.

(IV) (1) Describe what you would observe in test tube E.

(2) If the magnesium ribbon is replaced by

- copper strip,

- zinc strip.

Would the result be the same. Explain your answer.

(b) It is found that aluminium always tarnishes in air and no further corrosion occurs

even when placed in the salt solution in tube D. Explain.

( 17 marks )

4. (a) Describe how magnesium reacts with oxygen when heated?

(b) Write a chemical equation for the reaction in part (a). State symbols must be

shown.

(d) How can you test the gas in part (c)? What do you expect to observe?

(e) What would you expect to see when excess zinc metal is added to copper(II)

sulphate solution? Write a chemical equation for the reaction.

( 10 marks )

5. The bottom of pot, electrical cable and window frames shown below are made of

different metals.

Metal	Cost	Strength	Rate of corrosion	Thermal conductivity	Electrical conductivity	Abundance
A	Medium	medium	Slow	High	High	medium
B	Low	Low	Fast	High	High	High
C	High	High	Slow	medium	medium	High
D	Very high	Low	fast	medium	medium	Very low

Which metal shown in the table is most suitable for making

(I) the bottom of pot?

(II) window frames?

(III) electrical cable?

Give reasons for your choice.

( 6 marks )

6. A student carried out several experiments to investigate the order of reactivity of five

metals. The results are tabulated as follows.

Treatment of metal	Metal
Treatment of metal	A	B	C	D	E
Reacting with cold water	No reaction	No reaction	Slow reaction	Vigorous reaction	No reaction
Heating metal oxides with carbon	Metal A obtained	Metal B obtained	No reaction	No reaction	No reaction
Reacting with dilute hydrochloric acid	No reaction	No reaction	Hydrogen evolved	Hydrogen evolved	Hydrogen evolved
Displacement reaction	Metal A displaces metal B from a nitrate solution of metal B.

(a) Place the five metals in decreasing order of reactivity.

(b) Which of the five metals should be extracted by electrolysis of its molten

compound? Give a reason.

metal element. What is it? Suggest a name for this metal.

( 6 marks )

END OF PAPER