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CHEMISTRY
1.
Figure 1 shows a flame obtained from a Bunsen burner.
Flame
2.
3.
4.
(i) Name the type of flame.
(1mark) * Nym*
(ii) State one shortcoming of using this flame in heating substances in the laboratory.
(1mark) * Nym*
(iii) Explain how the above shortcoming can be overcome.
(1mark) * Nym*
The table below shows the first ionisation energies of elements Y and Z.
Element
Ionisation energy KJ/mole
Y
494
Z
418
What do these values suggest about the reactivity of Y compared to that of Z? Explain.
(2marks) * Nym*
a) Give the structural formula of
3,3-dimelthylpent-1-yne
(1mark) * Nym*
b) Name the following compounds using the IUPAC system
(i) CH3CH2CH2OOCCH3
(1mark) * Nym*
(ii)
CH3CH2CHC=CH2
Br CH3
(1mark) * Nym*
Figure 2 below shows the electrolysis of dilute hydrochloric acid.
Gas U
Gas v
Dilute
hydrochloric
acid
Inert electrodes
cell
(i) On the diagram, label the cathode and the anode.
5.
(1mark) * Nym*
(ii) Name the gases:(1mark) * Nym*
U …………………….
V …………………….
(iii) Write the half-cell equation for the reaction taking place at the anode. (1mark) * Nym*
Given the equation for reaction
2Al(s) + 3Cl2(g)
2AlCl3(s)
Calculate
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1
(i) Volume of chlorine ( at r.t.p) required to react with 3g of Aluminium (molar gas volume at r.t.p =
24 litres, Al=27, Cl=35.5)
(1 ½ marks) * Nym*
(ii) Mass of aluminium chloride formed.
6.
The structure of water molecules can be represented as shown below
(1 ½ marks) * Nym*
(i)
7.
8.
Name the bond type represented by letter X and W.
X ………………………………………………………………..
(1mark) * Nym*
W ………………………………………………………………
(1mark) * Nym*
(ii) Relative molecular mass of Methane and water are almost similar, however the boiling
point of water is 1000 while that of methane is -1610C. Explain
(1mark) * Nym*
State and explain what happens to the masses of the following substances when they are
separately heated in open crucibles
(3marks) * Nym*
(i) Copper metal
(ii)
Sulphur powder.
Two pieces of cotton wool were separately soaked in concentrated ammonia and hydrochloric
acid solutions respectively. Then, were simultaneously placed at the ends of an open-ended
tube as shown in figure
White deposit
9.
a) Name the white deposit.
(1mark) * Nym*
b) Work out the relative rates at which ammonia and hydrochloric acid gases diffuse.
(1mark) * Nym*
c) State the gas law that explains the difference in the rates of diffusion. (1mark) * Nym*
In the set-up in figure was used to separate a mixture of sulphur (IV) oxide and ammonia gases
SO2/NH3 gases
10.
11.
12.
T
Anhydrous calcium chloride
a) Name gas T.
(1mark) * Nym*
b) What is the intended function of anhydrous calcium chloride?
(1mark) * Nym*
a) What is half-life?
(1mark) * Nym*
b) If a radioactive isotope has a half-life of 2.5 hours, how long will it take for its mass to
reduce to 1/8.
(2marks) * Nym*
A compound of carbon, hydrogen and oxygen contains 71.1% by mass of oxygen, 2.2%
hydrogen and the rest is carbon. It has relative molecular mass of 90.
a) Determine the empirical formula of the compound.
(2marks) * Nym*
b) Determine the molecular formula of the compound.
(1mark) * Nym*
Study the flow chart and answer the questions that follow:Bromopropane
NaOH, Heat
Compound
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2
Reagent C
Propanoic
process
A
B
acid
Name
(i) Process A. ……………………………………
(ii) Compound B …………………………………
(iii) Reagent C ……………………………………
13. Study the diagram below and answer the questions that follow
(1mark) * Nym*
(1mark) * Nym*
(1mark) * Nym*
Cold water
A mixture of iodine and
sodium chloride
Wire
gauze
Heat
14.
15.
16.
17.
a) State and explain the observation to be made.
(2marks) * Nym*
b) What is the purpose of cold water in this set-up
(1mark) * Nym*
Some average bond energies are given below
Bond
Energy in KJmol-1
C–C
348
C–H
414
C1 – C1
243
C – C1
432
H – C1
340
Calculate the energy change for the reaction below
C2H6 + Cl2(g)
CH3CH2Cl2(g) + HCl(aq)
(3marks) * Nym*
Substance Q reacts with cold water to evolve hydrogen gas. When the hydrogen gas is passed
over heated substance R, the colour of R changes from black to brown and a colourless liquid
form at the cooler parts of the vessel.
(i) Identify substance
Q ……………………………….
(½ mark)
R ………………………………….. (½ mark)
(ii) State with reasons the type of reaction that takes place between hydrogen and R.
(2marks) * Nym*
Calculate the solubility of sugar in water at 400c from the following information.
Mass of evaporating dish
=
23.0g
Mass of evaporating dish + Sample of saturated solution =
192.0g
Mass of evaporating dish + solid after evaporation of solution = 142.0g
(2marks) * Nym*
a) Consider the forward reaction below.
NH+4(aq) + OH-(aq)
NH3(g) + H2O(l)
Which species that act as:(i) acid ……………………………………
(1mark) * Nym*
(ii) base ……………………………………
(1mark) * Nym*
b) The pH values of hydrogen sulphide solution and sulphuric acid are 6:5 and 1:0
respectively. Explain
(1mark) * Nym*
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3
18.
Below is a table of reduction potentials, in volts, of some half cells. The letters are not actual
symbols, but use then to answer the questions which follows
Reaction
Volts
A2+ + 2e
A(s)
-2.80
B+ + e
B(s)
-1.50
+
2C + 2e
C2(s)
0.00
D2 + 2e
2D -(s)
+ 3.20
+
G + e
G(s)
+ 1.80
Select the species with the highest
(2marks) * Nym*
(i)
19.
20.
oxidising power
(ii)
reducing power
Consider the zinc nuclide below:65
Zn
30
Determine the number of protons and neutrons in the nuclide.
(2marks) * Nym*
The diagram below is a set-up of apparatus that was used to study some property of ammonia
gas.
Cardboard
Hot platinum wire
Concentrated
ammonia
Explain the observations that was made.
(3marks) * Nym*
Determine the oxidation state of chlorine, in each of the following ions.
(2marks) * Nym*
ClO-3
ClO-4
22.
In an experiment, metal J reacts with cold water while K does not react with water at
all. Metal L reacts with an oxide of J to form metal J. What is the order of reactivity of the
three metals, starting with the most reactive?
(2 marks) * Nym*
21.
23.
Using reagents provided only, explain by means of balanced chemical equations how
you could prepare a salt of zinc carbonate solid.
(3marks) * Nym*
24.
- Zinc powder
- Nitric (v) acid (dilute)
- Water
- Solid sodium carbonate
A gas jar of hydrogen sulphide was inverted onto another gas jar of sulphur (IV) oxide as
shown in the figure below.
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4
Hydrogen sulphide gas
Sulphur (iv) oxide
a) State the condition for the two gases to undergo any possible reaction.
(1mark) * Nym*
b) Explain the observation that would be made if the above condition is set.
(2marks) * Nym*
25.
In two experiments, a given volume of air was reacted with excess magnesium and zinc
powder separately. In which of the two experiments was the change in the volume of air
greater? Give a reason.
(3marks) * Nym*
26.
A gas occupies a volume of 600cm3 at a pressure of 760mmHg and temperature of
250C. What volume would it occupy at a pressure of 780mmHg and a temperature of 500C?
(3marks) * Nym*
27.
28.
29.
30.
a) When is water said to be ‘hard’?
(1mark) * Nym*
b) State one method of removing
(2marks) * Nym*
(i) Temporary hardness
(ii) Permanent hardness
Painting, oiling, galvanising and or tin plating are methods of rust prevention.
a) Explain the similarity of these methods in the way they prevent rusting.
(1mark) * Nym*
b) Explain why galvanised iron objects are better protected even when scratched .
(1mark) * Nym*
The chemical equations below are the main reactions in large scale manufacture of sodium
carbonate.
NH3(g) + CO2(g) + H2O(l)
NH4HCO3(aq)
NH4HCO3(aq) + NaCl(aq)
NaHCO3(s) + NH4Cl(aq)
a) Explain how the two products, NAHCO3 and NH4Cl are separated.
(1mark) * Nym*
b) How is sodium carbonate finally obtained?
(1mark) * Nym*
(i) Explain how ammonia is recovered and recycled.
(1mark) * Nym*
Study the following equilibrium reaction
2A2(g) + B2(g)
2A2B(g) H = -197KJmol-1
Suggest two ways of increasing the yield of A2B.
(2marks) * Nym*
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