Chemistry 2009 PNEB (PUNTLAND NATIONAL EXAMINATION BOARD)

Name .............................................................

School ..................................…………………

Roll Number.........................………………….

Puntland State of Somalia

Ministry of Education

Puntland National Examination Board

Form 4

CHEMISTRY Examination

2009

Time 2 hours

Plus 10 minutes before the exam for reading through the paper

TOTAL TIME 2 hours 10 minutes INSTRUCTIONS TO CANDIDATES INSTRUCTIONS TO CANDIDATES This paper consists of 20 printed pages

Count them now. If there are any missing, inform the invigilator

There are two parts:

SECTION A – Multiple Choice Questions 10 Marks SECTION B – Structured Questions 90 Marks TOTAL 100 Marks

• Answer all questions • All answers and working must be written on this paper in the spaces provided

immediately after each question • Rough work can be done on page 2. This will not be marked • No extra paper is allowed • No calculators are allowed • If you make a mistake, cross out the incorrect answer and clearly write your

correct answer

Puntland National Examination Board Secondary School Form Four Examinations Puntland Certificate of Education Chemistry Examination June 2009

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Use This Page for Rough Work, It Will Not

Be Marked

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SECTION A: MULTIPLE CHOICE QUESTIONS (10 MARKS)

Instructions for this section:

• For each question in this section, circle the correct answer

• If you change your mind, cross out the wrongly chosen answer and clearly circle

the correct answer

• For each question there is only one correct answer

• If the examiner thinks you have marked two answers, you will not receive a mark

for that question.

1. Which of these reactions uses up oxygen?

A Addition

B Combustion

C Polymerization

D Cracking

2. Which of the following letters is correct for the symbol for Magnesium atom?

A MG B Mg

C mg D mG

3. What is the possible identity of the gases A and B in the experiment shown below?

A Ammonia and Hydrogen

B Ammonia and Hydrogen chloride

C Ammonia and Nitrogen

D Ammonia and Chlorine


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4. What is the Percentage mass of hydrogen in methane (C H 4

A 25% B 45%

) gas?

C 15% D 75%

5. The four tubes show an investigation of rusting. Each one of these four tubes

contains a nail and the reagents indicated.

In which tube would the nail rust first?

A 1

B 4

C 3

D 2

6. In the reaction below, what is So2

2 Mg acting as?

(s) + SO2 (g) 2 MgO (s) + S

(s)

A A catalyst

B An oxidizing agent

C An acid

D A reducing agent


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7. This box shows the reactivity of some elements.

Which metal from the table above is most likely to be found uncombined in the earth’s

crust?

A Copper

B Lead

C Zinc

D Magnesium

8. Which of the following is not true for ammonia?

A It has a sharp or pungent smell

B It can be collected over water

C It turns universal indicator solution from green to blue

D It is less dense than air

9. Chemical formula for Aluminium Sulphate is

A AlSO4

B (Al)

2 SO4

C Al (SO

4)

D Al3

2 (SO4)

3

Magnesium Most Reactive Zinc Iron Increasing reactivity Tin Lead Copper Least Reactive


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10. Study the diagram below and use it to answer the question.

Solid W Liquid

Gas

What process is represented by letter W? A Evaporation

B Sublimation

C Freezing

D Melting


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SECTION B: STRUCTURED QUESTIONS (90 MARKS) Question 1 (10 marks) a) The diagrams below show the arrangement of particles in the three different states of

water.

A B C

Identify what state each letter represents. (3 marks)

A……………………………….……………

B…………………………………………….

C…………………………………………….

b) Classify the following as either physical or chemical change.

i. Fermentation of beer (1 mark)

……………………………………………..

ii. Rusting of iron (1 mark)

…………………………………………….

iii. Dissolving of table salt (1 mark)

…………………………………………….

iv. Heating of ice (1 mark)

…………………………………………….


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c) A student extracted red colouring from four different plants, R, S, T, and U and put a

spot of each colouring on a filter paper. The filter paper was dipped into a solvent and

left for 30 minutes. See the results in the diagram below.

i) What is the name given to the separation process shown in the diagram? (1 mark)

………………………………………………………………….

ii) Which plant contained the greatest number of different pigments? (1 mark)

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iii) Which two plants contained the same pigments? (1 mark)

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Question 2 (7 marks)

a) The diagram shows how paraffin oil vapour can be cracked (broken down) in the

laboratory.

i. What is the function of the aluminium oxide in this experiment? (1 mark)

…………………………………………………………………………..

ii. Give one advantage of cracking paraffin. (1 mark)

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iii. Two gases collected in the gas jar are displayed below. Identify them. (2 marks)

H H H H H

Ι I I I I

H---C-----C-----C----H C = C

I I I I I

H H H H H Gas A__________________ Gas B_________________

b) The equations below illustrate three typical reactions of alkanes.

i. CH3 CH3 + Cl2 light CH3 CH2

Cl + HCl

ii. 2 CH3 CH3 + 7 O 2 heat 4 CO 2 (g) + 6 H 2 O

(l)

iii. CH2 = CH2 + H2 Ni(s) CH3 CH

1303

oC – 150o

C

Name the type of reaction in each equation: (3 marks)

i.…………………………………………………………………………………….

ii.……………………………………………………………………………………

iii. ……………………………………………………………………………………..

Question 3 (10 marks)

a) Look at the pH scale below for some solutions found in the laboratory.

i) What would be the pH value for a very strong acid? (1mark)

……………………………………………………

ii) What would be the pH value for a very strong alkaline solution? (1 mark)

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1 2 3 4 5 6 7 8 9 10 11 12 13 14


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iii) What would be the pH value for a neutral solution? (1 mark)

…………………………………………………….

b) Complete the following word equations

i. Acid + Metal …………………………………..

………………………………………………………………………... (2 marks)

ii. Hydrochloric Acid + iron

…………………………………………………………………………………… (2 marks)

c) What is the concentration of 100 cm3

moles? (Na = 23, H = 1, O = 16) (3 marks)

of a solution of sodium chloride containing 0.04

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Question 4 (7 marks) a) Ammonia is produced through the Haber process where conditions are designed to

make it quickly and cheaply. Study the graph and answer the questions that follow.

i. If the Haber process is carried out at 400o

what percentage of ammonia will be at equilibrium? (1 mark)

C, at a pressure of 200atm, approximately

………………………………………………………………………………………………….

ii. What effect does decreasing the temperature have on the yield of ammonia?

(1 mark)

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b) Nitrogen (II) oxide readily reacts with oxygen to form nitrogen (IV) oxide. The

following is an energy-level diagram for the reaction.

i. What does each of the following represent? (3 marks)

ΔH1

ΔH

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2

ΔH3…………………………………………………………………………

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ii. What is the sign on ΔH3

………………………………………………………………………………………………….

? (1 mark)

iii. Write an expression for ΔH3 in terms of ΔH1 and ΔH2

………………………………………………………………………………………………….

(1

mark)

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Question 5 (8 marks) Study the table below and use the information to answer the questions that follow:

Substance

Electrical Conductivity Melting

point

Boiling point

0c Solid Molten In water

A Good Good Does not dissolve 1540 2760

B Poor Poor Poor 0 100

C Poor Good Good 808 1465

D Good Good Makes an alkaline solution 98 890

a) Choose one metal which, at room temperature, (200

i. Solid (1 mark)

C) is:

…………………………………………………………………………

ii. Liquid (1 mark)

……………………………………………..

b) i. Which substance is an ionic compound? (1 mark)

…………………………………………….

ii. Give reasons to your choice. (2 marks)

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c) i. Which substance could be an element of group I metals? (1 mark)

……………………………………………

ii. Give reasons to your choice. (2 marks)

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Question 6 (10 marks) The table below is about investigations of metal reactivity:

Metal

Solution to which metal is added

Magnesium

Chloride

Iron

Sulphate

Lead

Nitrate

Copper (I)

Sulphate

Silver

Nitrate

Magnesium

Iron X

Lead X X X

Copper X X X

Silver X X X X

Look at the table carefully and notice that:

The cross ( X ) is used to show if a less reactive metal is displaced from solution. The

tick ( ) is used to show if there is no reaction.

a) Fill the table by putting ( ) or ( X ) in the appropriate blanks. (4 marks)

b) An iron nail is placed in a Copper (II) Sulphate solution. The equation for the reaction

is;

Fe (s) + CU SO 4 (aq) Fe SO 4 (aq) + CU

(s)

i. Write an ionic equation for the reaction. (2 marks)

…………………………….……………………………………………..

ii. Write reduction half equation. (2 marks)

……………………………………………………………………………

ii. Write oxidation half equation. (2 marks)

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Question 7 (10 marks) Carbon exists in two crystalline allotropic forms shown in the diagram below.

I II

a. i) Name the allotropes labeled (2 marks)

I…………………………………………………

II…………………………………………………

ii) Give one use of the allotrope in (I) above. (1 mark)

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iii) Which allotrope has its carbon atoms bonded to four other carbon atoms? (1 mark)

……………………………………………

b) Give reason(s) for the following statements, identifying in each case, the allotrope

being referred to.

i. One allotrope conducts electricity while the other does not. (2 marks)

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ii. One allotrope is soft and slippery while the other is very hard. (2 marks)

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iii. One allotrope has a lower density than the other. (2 marks)

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Question 8 (11 marks) This diagram shows the apparatus used to find out the effect of an electric current on a

concentrated aqueous solution of sodium chloride.

a) i. What is electrolysis? (2 marks)

………………………………………………………………………………………………………

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ii. On the diagram label the electrodes. (2 marks)

b) State three things you will observe when the circuit is switched on. (3 marks)

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c) i. Name the product at the positive electrode. (2 marks)

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ii. State a test for this product and the result of the test. (2 marks)

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Question 9 (7 marks) a) The diagram below shows part of periodic table. The letters do not represent the

actual symbols elements.

a

b

d

e f

i. Which element is in group 4? (1 mark)

………………………………………………………..

ii. Which element is in the second period? (1 mark)

………………………………………………………

iii. Which element is a noble gas? (1 mark)

………………………..……………………………..

iv. Which element is a metalloid? (1 mark)

…………………………………………………….

v. Give two (2) elements that are non-metals? (2 marks)

…………………………………………………….

vi. Which element is likely to be a gas? (1 mark)

……………………………………………………


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Question 10 (10 marks) Ali collected some water from a polluted river.

The water contained soluble solids and insoluble clay and had a pH of 5.

a) How can Ali separate the clay from the rest of the river water? (1 mark)

…………………………………………………………………………..

b) What will be the effect of this water on litmus paper? (1 mark)

…………………………………………………………………………..

c) Ali then boiled the river water to obtain the soluble solids. The diagram below

shows how he heated the water.

Which of the substances named in the diagram is

i. an alloy? (1 mark)

………………………………………………………………

ii. a compound which is liquid at room temperature? (1 mark)

………………………………………………………………

iii. an element? (1 mark)

……………………………………………………………….

iv. a fuel? (1 mark)

………………………………………………………………


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d) Name the main substance in natural gas? (1 mark)

………………………………………………………………

e) What is the normal temperature of boiling water? (1 mark)

………………………………………………………………

f) After Ali boiled off the water, he analysed the white powder on the inside of the

steel can. The table shows his results.

Name of ion Formula of ion Mass of ion present / milligrams

Calcium Ca 16 2+

Carbonate CO3 35 2-

Chloride Cl 8 -

Nitrate NO3 4 -

Sodium Na 8 +

Sulphate SO4 6 2-

i. Which positive ion had the greatest concentration in the sample of river water?

………………………………………………………………… (1 mark)

ii. Complete the following equation to show how a sodium ion is formed.

Na Na+

+ …………………. (1 mark)

END