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231/1
Chemistry
Paper 1
2 Hours
June 2010
KASSU JOINT EVALUATION TEST (J.E.T)
Kenya Certificate of Secondary Education (K.C.S.E)
Instructions to candidates.
 Write your name and index number in the spaces provided above.
 Sign and write the date of examination in the spaces provided above.
 Answer ALL the questions in the spaces provided.
 Mathematics tables and silent electronic calculators may be used.
 All working MUST be clearly shown where necessary.
For Examiner’s use only.
Questions
1-31
Maximum score
80
Candidates score
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1.
2.
3.
4.
100 cm3 of 0.1M ethanoic acid solution has a different pH value from less than of
100 cm3 of 0.1 hydrochloric acid. Explain.
(2mks)
In the chemical equation below identify the base and give a reason for your
choice.
(1 mk)
C2H5O- (aq) + H2O(l)  C2H5OH(aq) + OH—(aq)
Salt Q has a solubility of 25g/100g of water. 40g of salt Q is stirred in 45g of a
solution which contains 5g of salt Q. how much more of salt Q will dissolve in the
solution.
(21/2mk)
Study the sequence of reactions below and answer the questions that follow.
(a)
(b)
5.
Write the formulae of substance T.
Write balanced chemical equations for steps 2 and 3.
Step 2:
Step 3:
Study the reaction scheme below.
(a)
(i)
(ii)
(1 mk)
(1mk)
(1mk)
Identify the possible cation present in the solution containing metal
chloride.
(1mk)
Write an ionic equation between the metal ion and excess NaOH
solution.
(1mk)
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6.
Study the reaction scheme below and use it to answer the questions that follow.
(a)
(b)
(c)
7.
(a)
(b)
Name the catalyst used in:
Step 1:
Step 2:
A …………………. (½ mk)
X ………………..
(½ mk)
B …………………. (½ mk)
Y ………………..
(½ mk)
C …………………. (½ mk)
Z ………………... (½ mk)
Write a balanced chemical equation for the reaction between excess
aqueous solution of compound B and silver chloride.
(1mk)
Write the structural formula of
(i)
3, 3-dimethy/pentane.
(1mk)
(ii)
2-bromo-4-methyl pentan-2-ol
(1mk)
Below is the structure of polysty erene.

8.
9.
H

C 

C6H5
H
H


C  C 


H
C6H5
H
H


C  C 


H
C6H5
H

C

H
Draw the monomeric unit of polystyrene.
(1mk)
The flame produced from the Bunsen burner when the air-hole is completely
closed is sooty and bright yellow. Explain why.
(2mks)
(i)
A form one student from KASSU high school was interested in
determining the components in a spinach leave that makes it have the
green colouration. He set to do some experiment. State the two methods of
separation that the pupil will apply in the right sequence to get the results.
(2mks)
(ii)
How can the pupil ascertain the purity of each component obtained? (1mk)
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10.
11.
12.
13.
14.
15.
The table below shows the atomic and ionic radii of some period three elements.
Atomic radius (nm) Ionic radius (nm)
X
0.186
0.175
0.160
0.135
0.104
0.184
From the table. Identify:
(a)
Strongest reducing agent.
(1mk)
(b)
The bond between the atoms of X.
(1mk)
(c)
An element whose oxide has a pH of above seven.
(1mk)
69
71
Natural gallium consists of the isotopes Ga and Ga in the ratio 3:2
respectively. Which of the isotopes is likely to depict the relative atomic mass of
gallium? Explain.
(2mks)
A radioactive element X decays as shown below.
216
218
X
Pb + a + b
84
82
Determine the value of a and b in the equation.
(2mks)
(a)
Sulphur atomic number 16 and oxygen atomic number 8 are elements in
group 6 of the periodic table. Sulphur is a solid at room temperature while
oxygen is a gas at room temperature. Explain why hydrogen sulphide with
molecular mass 34 is a gas at room temperature while water with
molecular mass 18 is a liquid.
(2mks)
(b)
An element x forms a bromide that is a liquid at room temperature and that
has the formula XBr3. Neither the element nor its bromide conducts
electricity.
(i)
State the group in which X is likely to be found in the periodic
table.
(1mk)
(ii)
State the oxidation state of X in XBr3.
(1mk)
A mass of 25.6g of tin was deposited on the cathode when electricity was passing
through the electrolyte for two hours fifteen minutes. Determine the current used
during the experiment. (Sn2+ = 118, IF = 96500C)
(2mks)
Study the table below consisting of reduction potential of the elements (not actual
symbols) and answer the questions that follow.
Element e.mf. (v)
V
+1.10
W
+0.78
X
+0.47
Y
+0.00
Z
-0.46
(a)
Calculate the e.m.f. of a cell obtained when W and Z half cells are used.
(1mk)
(b)
Given that Wand Z have valencies 2 and 1 respectively, give the cell
reaction and cell representation for the cell.
(2mks)
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16.
17.
Determine the enthalpy of formation of methane using the data given below.
Hc Kjmol-1
Combustion of carbon
-393
Combustion of hydrogen -286
Combustion of methane -890
(3mks)
In order to determine the relative molecular mass of unknown hydrocarbon, the
following results were obtained.
Mass of evacuated flask
= 84.64
Mass of flask filled with nitrogen gas = 84.92
Mass of flask filled with hydrogen = 85.42
18.
19.
20.
21.
22.
R.A.M. of nitrogen = 14. All observations were made at room temperature and
pressure (molar gas volume at RTP = 24000 cm3).
(a)
Calculate the number of moles of nitrogen gas.
(1mk)
(b)
What is the relative molecular mass of unknown hydrocarbon? (2½ mks)
The diffusion of molecules of ammonia and an unknown gas B through air was
investigated. The distance covered by the two gases is shown by the apparatus
below. A white ring indicated appeared after 4 minutes.
Calculate the molar mass of B.
(N = 14, H = 1)
(i)
What is an alloy?
(ii)
Give an example of an alloy, its use and the elements it contains.
Name of alloy Components Use
(2mks)
(1mk)
(2mks)
A concentrated solution of sulphuric contains 70% H2SO4 and has density of
1.8g/cm3. Determine the molarity of the sulphuric acid solution. (H=1, S=32,
O=16)
(2mks)
Aqueous ammonia is added to copper (II) sulphate solution drop wise. A blue
precipitate is formed; on adding excess ammonia the precipitate dissolves to give
a deep blue solution. Explain the above observations by writing equations. (3mks)
(a)
calculate the relative atomic mass of a metal M given that 0.65g of the
metal forms 1.61g of sulphate of formula MSO4.. (S = 32, O = 16). (2mks)
(b)
Given that the phosphate ion has formula PO43-, write the formula of the
phosphate of metal M.
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23.
24.
In the following half reaction, calculate the change in oxidation state of chromium
Cr2O72-(aq) + 14H+(aq) + 6e  2Cr3+(aq) + 7H2O(l)
(1mk)
The diagram below represents the set up to investigate the reaction between Iron
(II) sulphide and dilute sulphuric acid. As the reaction proceeded, the mass of the
beaker and its contents was recorded at regular time intervals.
(i)
(ii)
25.
26.
27.
28.
29.
Write the equation of reaction that took place.
(1mk)
Sketch and explain the curve you would obtain if the balance reading is
plotted against time.
(2 ½ mks)
An acid-base indicator is a substance with specific colour for both acidic and
alkaline medium. A particular indicator used in science laboratory attains the
following equilibrium state.
XOH
X=(aq) + OH-(aq)
(Blue)
(Red)
State and explain the colour of this indicator when added to:
(a)
Wood ash solution.
(2mks)
(b)
Vinegar solution
(2mks)
Carbon has got reducing properties just like one of its oxides. Use dots (.) and
crosses (x) to represent the bonding in the molecule of this oxide. (C = 6, O = 8).
(2mks)
Water gas is a mixture of carbon (II) oxide and hydrogen gas and producer gas is
a mixture of carbon (II) oxide and nitrogen gas are one of the fuels used during
world war.
(i)
Explain why water gas is a better fuel than producer gas.
(2mks)
(ii)
State two factors to consider in choosing a fuel for a space rocket. (1mk)
Boiling points of alkanols are higher than those of hydrocarbons of approximately
same molecular mass. Explain.
(1mk)
(i)
Usually, zinc ore is found mixed with lead ore. What property of zinc
makes it possible to separate it from its mixture with lead metal? (1mk)
(ii)
Extraction of copper from copper pyrites involves the following the
processes:
(a)
Crushing the ore.
(b)
Mixing the crushed ore with water and oil then bubbling air
through it.
(c)
Roasting the ore.
(I)
What name is given to procedure (a) to (b) and what is its role?
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30.
31.
Name:
(½ mk)
Role:
(½ mk)
(II)
State one use of copper.
When a wet red coloured flower petals are dropped in a gas jar full of sulphur
(IV) oxide gas, they get discoloured. When wet red and blue litmus papers are
placed in a gas jar full of chlorine gas are also discoloured (bleached). Using
relevant equations explain the difference in the two modes of bleaching. (3mks)
Study the diagram below and answer the questions that follow.
When some hydrogen chloride gas is allowed into water and the mixture stirred,
the bulb lights and gases X and Y are formed.
(i)
Name gas
X:
(½ mk)
Y:
(½ mk)
(ii)
Explain why the bulb does not light before the hydrogen chloride gas is let
into the water.
(1mk)
(iii) Explain using equations why the volume of gas X is less than that of gas
Y.
(2mks)
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