1. Diagram 1 shows the symbol of the atoms of element X , element Y and element Z . The letters used are not the actual symbols of the elements.

23 16 35

X Y Z 11 8 17

Diagram 1a) State the proton number of the atom of element X

_________________________________________________________________________[1 mark]

b) Which element is a halogen? Explain

.....................................................................................................................................................[2 mark]

c) i) Identify the position of element Y in Periodic Table of Elements

_______________________________________________________________________[1 mark]

ii) Explain why element Y is placed at the position identified in d(i)

_______________________________________________________________________[1 mark]

d) i) Write the formula of the compound formed between element X and Y

_______________________________________________________________________[1 mark]

ii) State two physical properties of the compound formed in e(i)

_______________________________________________________________________

_______________________________________________________________________[2 marks]

iii) Draw the electron arrangement of the compound formed in e(i)

[2 marks]

2. Diagram 2 shows the apparatus set up for two types of cells, P and Q

Diagram 2

a) State one difference in energy change between cell P and cell QIn cell P energy change is from ....................................................to ..............................

In cell Q energy change is from ....................................................to ..............................

[1 mark]

b) What is the product at the anode in cell P?___________________________________________________________________________

[1 mark]c) Write the half equation for the discharge of cation in cell P

__________________________________________________________________________[1 mark]

d) State one observation at electrode zinc in cell Q

__________________________________________________________________________[1 mark]

e) Diagram 2.2 shows the apparatus set-up for the electrolysis of sodium chloride solution using carbon electrodes

i) State all ions attracted towards electrode P and Q

Electrode P Electrode Q

[2 marks]ii) State which ion discharge at electrode Q. Explain why

_______________________________________________________________________

_______________________________________________________________________[2 marks]

iii) Describe one chemical test to identify gas X_______________________________________________________________________

_______________________________________________________________________[2 marks]

Total mark =10m

3)

Diagram 3 shows a series of reaction of compound P. Compound P and compound Q are shown in condensed structural formulae.

(a) Compound P is propene . State the homologous series of compound P

_________________________________________________________________

[1 mark]

(b) Compound Q is used as a cooking gas.

i) State the molecular formula of compound Q ....................................................... [ 1 mark]

ii) Write a chemical equation for the combustion of compound Q to produce carbon dioxide and water

___________________________________________________________________

[2 mark]

Diagram 3

Steam and

Phosphoric acid

Compound Q

CH3CH2 CH3

Compound P

CH2=CHCH3

Compound R

Compound S

CO2 + H2O

I

II

III

Combustion

+ Ethanoic acid

+ concentrated sulphuric acid

(c) Compound P can be changed to compound R which is an alcohol through process II.

Name process II ............................................................................................ [ 1mark]

State the general formula for alcohol _____________________________________[1 mark]

(d) Explain briefly how compound S can be prepared from compound R in laboratory.

In your answer include the appropriate reagents and condition for the preparation.

__________________________________________________________________

__________________________________________________________________

__________________________________________________________________

[3 marks]

(e) An organic compound W has a molecular formula of C4 H8 . Compound W has 3 isomers.

Draw two structural formulae of two isomers of W

[2 marks]

Total mark= 11m

Max mark=10m

4) Natural rubber is a polymer, where the monomer is isoprene or 2- methylbuta-1,3-diene. Natural rubber is obtained from latex, which is a colloid made up of rubber particles and water.

a) Draw i) Structural formula of isoprene (1m)

…………………………………………………………………………labelled diagram of latex particle in water (2m)

…………………………………………………………………………

b) Explain why latex in the original form does not coagulate (2m)

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

……………………………………………………………………………......................…………c) However, or when latex is exposed to air, coagulation of latex occur. Explain (3m)

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

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

………………………………………………………………………………...............................…………d) The properties of natural rubber can be improved by treating it with sulphur.

i) Name this process (1m)

…………………………………………………………………………

ii) State ONE use of the treated rubber above (1m)

………………………………………………………………………

Total= 10m

5.

Diagram 5

Diagram 5 above show the experiment to determine the heat of precipitation of barium sulphate. 50 cm3 of 1.0 mol dm-3 potassium sulphate solution and 50 cm3 of 1.0 mol dm-3 barium chloride solution are poured into two separate polystyrene cups. Then both solution are added. The results are shown as below

a) What is meant by the heat of precipitation of barium sulphate?

[1 mark]

b) Write an ionic equation for the reaction

Initial temperature of potassium sulphate = 29.5 oC

Initial temperature of barium chloride = 29.5oC

Maximum temperature of mixture = 34.50C

Barium Chloride solution

Potassium sulphate solution

_______________________________________________________________ [1 mark]

c) State one observation for the experiment

[1 mark]

d) Calculate i. The heat released in the experiment[Specific heat capacity of water = 4.2 Jg-1oC-1, Density of water = 1.0 g cm-3]

[2 mark]ii. The number of moles of barium sulphate formed

[1 marks]iii. The heat of precipitation of barium sulphate

[2 marks]

e) Draw the energy level diagram for the precipitation of barium sulphate

[2 marks]

Total =10m

-----END OF QUESTIONS-----

Standardised test form 5 –sem1 – 2011 chemistry = suggested answers

No. Answers Mark1. a) 11 1b) Z

Because the valence electron Is 711

c)i) Group 16, Period 2 1ii) It has 2 shells occupied with electrons and the valence

electron is 61

d)i) X2Y 1d)ii) -soluble in water

-insoluble in organic solvent-can conduct electricity in aqueous and molten state-high melting and boiling point

2

d)iii)

-Correct no of shells-correct no. of electron on each shell and charge

2

No. Answers Mark2. a) Cell P: Electrical energy Chemical energy

Cell Q: Chemical energy Electrical energy1

b) Oxygen and water 1c) Cu2+ + 2e Cu 1d) Zinc electrode becomes thinner 1e)i)

Electrode P Electrode QH+ , Na + Cl - , OH -

2

ii) Chloride ion because the concentration of chloride ion is 2

higher than hydroxide ioniii) Put the burning/lighted wooden splinter into the test tube, a

‘pop’ sound produced2

Scheme answer no 3

Question Suggested Answer marks

3 a. Alkene 1m

b .i C3H8 1m

ii C3H8 + 5O2 3 CO2 + 4 H2O 2m

c. i Hydration 1m

ii Cn H2n +1 OH n=1,2,3…… 1m

d 1. ethanol is added into ethanoic acid and shake/stir [ volume ratio ethanol : acid = 2:1 ]2. a few drop of concentrated sulphuric acid is Added3. mixture is heated gently

1m

1m

1m

0

2m

Question Suggested Answer marks

2m

C – C = C – C

H

H

H

H H H

H

H

C – C = C – H

H

H

HH

H

H

H

C

Total mark= 10m

4) Natural rubber is a polymer, where the monomer is isoprene or 2- methylbuta-1,3-diene. Natural rubber is obtained from latex, which is a colloid made up of rubber particles and water.

No question Answers marks

4) a)

i)

Structural formula of isoprene

1

ii) Labelled diagram of latex particle in water

Correct diagram =1

Label = 1

b Explain why latex in the original form does not coagulate

Protein membrane of rubber particles are negatively charged

So, the particles repel each other and do not collide/ the protein membrane do not break

1

1

c However, or when latex is exposed to air, coagulation of latex occur. Explain (3m)

Air contain bacteria which produce lactic acid /hydrogen ions in latex

The hydrogen ions neutralise the negatively charged membrane

Rubber particles * reject rubber molecule or rubber polymers* become neutral and so they collide with each other

The membranes break, rubber molecules/ polymers combined *

1

1

1

C = C - C – C

H

H

H

H H H

H

H

reject rubber particles* 1

(4 marks maximum 3)

d The properties of natural rubber can be improved by treating it with sulphur.

(i) Name this process Vulcanisation ( correct spelling) 1

(ii) State ONE use of the treated rubber above

For making tyres, mattress, foam, shoes or any suitable answers

1

Total= 10m

Scheme answer no 5

Question Suggested Answer marks

5a. Heat change when 1 mole of Barium Sulphate form from its ions 1m

b Ba 2+ + SO4 -2 BaSO4 1m

c White observation forms or The containers become warm 1m

d.i Heat release = 100 x 4.2 x (34.5- 29.5) J = 2100J 2m

ii Mole of BaSO4 = 50 x 1.0 /1000 = 0.05

1m

iii0.05 mole BaSO4 - 2100 J1 mole BaSO4 - 1/ 0.05 x 2100 J - 42000 J ∆ H = -42kJ mol-1

1m

1m

e

2m

Total 10m

Energy

∆ H = -42 kJ mol-1

Ba 2+ + SO4 -2

BaSO4