233/2
CHEMISTRY
THEORY
1.
One mole of Heptane was thermally cracked, two hydrocarbons Q and P were formed. Q was
alkene molecule with three carbon atoms.
(i) (a) Give the molecular formula of:
Q
1mk*Nrk*
P
1mk*Nrk*
b) Write the structural formula of hydrocarbons.
Q
1mk*Nrk*
P
1mk*Nrk*
c) Name the compounds that can be used to prepare Ethene in the laboratory.
(1mk) *Nrk*
d) Name the compound formed when Q undergoes self addition reaction.
(1mk) *Nrk*
e) State one disadvantage of using the product named in (i) (d) above.
(1mk) *Nrk*
ii) An organic compound J has the following percentage by mass, carbon, 64.86%, hydrogen,
13.51% and the rest oxygen. The relative molecular mass of the compound is 74.
[C=12. H=1 O=16]
a) Work out the molecular formula of compound J.
(3mks) *Nrk*
b) To which homologous series does compound J belong?
(1mk) *Nrk*
c) Write a balanced chemical equation for the reaction that occurs when compound J reacts
with sodium metal.
(1mk) *Nrk*
d) Name the type of reaction indicated in ( c ) above.
(1mk) *Nrk*
e) (i) Name the organic compound formed when compound J reacts with excess acidified
potassium manganate (VII).
(1mk) *Nrk*
ii) State the observation made in (e) (i) above.
(1mk) *Nrk*
2.
The diagram below shows industrial extraction of aluminium
Molten alumina +
cryolite
Graphite anode
Molten
aluminium
a) Name and write the formulae of the major ore for this process.
Name
Formula)
b) Write the equation of the reaction taking place at the:
Anode
Cathode
c) Write the formula of the molten alumina.
d) State the role of cryolite added to molten alumina
e) It is cheaper to recycle aluminium other than to extract it. Explain.
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1
(1mk) *Nrk*
(1mk) *Nrk*
(1mk) *Nrk*
(1mk) *Nrk*
(1mk) *Nrk*
(1mk) *Nrk*
3.
f) Explain why graphite anodes must be replaced after some time.
(1mk) *Nrk*
g) State one property of aluminium that makes it suitable for wrapping food.
(1mk) *Nrk*
h) Aluminium is high in the reactivity series yet it does not react with both acid and air.
Explain.
(1mk)
i) When a current of 3 A is passed through fused aluminium oxide for 4 hour 30 minutes,
calculate the mass of aluminium obtained. [Al=27, 1F=96500C]
(2mks)
2.5g of a metal carbonate, MCO3 was reacted with excess 2M nitric (v) acid, the volume of
carbon (IV) oxide evolved measured and recorded at 10 second intervals. The results were
recorded as shown in the table below.
Volume of gas
0
90
150
210
280
305
390
450 480 480 480
(cm3)
Time in seconds
0
10
20
30
40
50
60
70
80 90 100
a) (i) On the grid provided, plot a graph of volume (vertical axis) against time. Label curve –
A
(3mks) *Nrk*
(ii) From your graph, determine the rate of reaction between 25 seconds and 40 seconds.
(2mks) *Nrk*
(iii) On the same grid, sketch a curve that would be obtained if the same experiment was
repeated using excess 1M Nitric (V) acid. Label the curve B.
(1mk) *Nrk*
(iv) Given that carbon (IV) oxide was measured at room temperature and pressure, work out
the relative atomic mass of metal M. (MGV = 24dm3, C= 12, O=16)
(3mks) *Nrk*
b) Students from St. Mary’s Girls set up an experiment to investigate a factor that affects
reaction rate as shown below.
Set up I
Lump of
marble chips
4.
Set up II
1M HCl solution
Fine powder of
marble chips
Both set ups produced bubbles, but in set up II, the bubble production was faster than in set up
I. explain.
(2mks) *Nrk*
The set up below was used to prepare hydrogen chloride gas and salt T.
Liquid M
Aluminium
powder
Salt T
Gas V
Flask I
heat
Flask II
Sodium
heat
chloride
a) crystals
Identify the following
Conc.
Sulphuric
(VI) acid
i)
Liquid M
ii)
Gas V
iii)
Salt T
b)Write balanced chemical equations for reactions that occur at
i) Flask I
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2
water
½ mk*Nrk*
½ mk*Nrk*
½ mk*Nrk*
(1mk) *Nrk*
5.
ii) Combustion tube.
(1mk) *Nrk*
c) Name the process that formed salt T as shown in the diagram.
( ½ mks) *Nrk*
d) Sulphuric (VI) acid is used as a drying agent in this experiment. Explain why calcium
oxide is unsuitable for the same purpose in this reaction
(2mks) *Nrk*
e) The water in the beaker was found to have a pH of 2.0 at the end of the experiment.
Explain.
(1mk) *Nrk*
f) Calculate the mass of salt T formed if 480cm3 of hydrogen chloride gas measured at r.t.p
was reacted with aluminium powder. (Al=27, Cl = 35.5, MGV=24dm3) (2mks) *Nrk*
g) In the space provided below, draw a well labelled diagram showing how you would
dissolve hydrogen chloride gas in water.
(1mk) *Nrk*
h) Explain why hydrogen chloride gas dissolved in methylbenzene does not react with calcium
carbonate.
(1mk) *Nrk*
i) Using equation, state the observation made when a gas jar containing hydrogen chloride gas
is opened near an open bottle of liquid ammonia.
(1mk) *Nrk*
a) Use the reduction potentials below to answer the questions that follow.
E volts
2+
Q (aq) + 2e
Q(s)
- 2.38
+
B (aq) + e
B(s)
- 1.14
D2+(aq) + 2eD(s)
+ 0.80
Fe3+(aq) + 3eFe(s)
-1.66
+
C (aq) + e
C(s)
- 0.76
(i) Select the strongest reducing agent. Explain.
(1mk) *Nrk*
(ii) Calculate the e.m.f value of electrochemical cell obtained when elements B and D are
paired together.
(1mk) *Nrk*
(iii) Write an ionic equation for the reaction that occurs when metal Q is immersed into a
solution containing C+(aq) ions.
(1mk) *Nrk*
(iv) State and explain whether the reaction given below occurs or not.
3B(s) + F3+(aq)
F(s) + 3B+(aq)
(2mks) *Nrk*
(b) Magnesium metal was connected to an underground pipe made of iron as shown below.
Grass
soil
Iron pipe
Magnesium rod
Its necessary to carry out the process shown above. Explain
(2mks) *Nrk*
(c ) Aqueous copper (II) sulphate was electrolysed using the set up shown below.
Battery
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Switch
Carbon electrode B
Carbon electrode A
Aqueous copper (II)
sulphate
6.
7.
(i) When the switch was closed, a gas was produced at electrode B, which electrode is the
anode?
(1mk) *Nrk*
(ii) Write the half equation for the reaction at electrode B.
(1mk) *Nrk*
(iii) State and explain the observation that will be made at electrode A.
(1mk) *Nrk*
(iv) What happens to the pH of the electrolyte above during electrolysis. Explain
(1mk) *Nrk*
d) If carbon electrodes were replaced with copper electrodes in the reaction in (a) above.
Write down the cathode and anode half equations which would occur.
Anode:
(1mk) *Nrk*
Cathode
(1mk) *Nrk*
The grid below represents part of the periodic table. The letters do not represent actual
symbols of the elements.
Q
R
N
U
T
S
M
V
L
P
J
a) (i) Write the formula of the compound formed between elements M and L.
(1mk) *Nrk*
ii) State the bond type and structure of the compound you have written in (a) (i) above.
Bond type:
(1mk) *Nrk*
Structure:
(1mk) *Nrk*
b) Select the element which is the most reactive metal. Explain
2mks) *Nrk*
c) Compare the atomic sizes of elements T and L. Explain.
2mks) *Nrk*
d) Explain why the chloride of V fumes in damp air.
(1mk) *Nrk*
e) Element U is more reactive than L. Explain
(1mk) *Nrk*
Study the flow chart below starting from iron metal.
Compound B
Fe3O4(s) + Gas V
Step 1
Chlorine gas
Fe2O3.3H2O
Air
Moisture
Step 2
Fe(s)
Step 4
Steam
Hot conc. H2SO4
Step 3
Fe2[SO4]3(aq) + H2O(l) + gas D
Sulphur heat
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Compound T
Step 5 dil. HCl(aq)
Solid x
Step 6
(i) NaOH(aq)
(ii) Filter
FeCl2
gas L
step 7
H2O2(aq)
Step 8
(i) NaOH
(ii) Filter
Brown solution
Solid V
step 9
heat
Solid A
(a) Name gases
( 1 ½ mks) *Nrk*
D
L
V
(b) Identify the following substances.
2 ½ mks) *Nrk*
(i) Compound B
(ii) Compound T
(iii) Solid A
(iv) Solid V
(v) Solid X
c) What name is given to the reaction in step 2?
1 mk) *Nrk*
d) State the colour of solid X
1 mk) *Nrk*
e) Write balanced equations for the reactions that occurred in
Step 1
(1mk) *Nrk*
Step 5
(1mk) *Nrk*
f) What property of hydrogen peroxide (H2O2) is indicated in step 7 of the flow chart? (1mk) *Nrk*
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