1
THE AMKA CHEMISTRY EXAMINATION
Kenya Certificate of Secondary Education
233/1 - CHEMISTRY - Paper 1
(Theory)
JUNE 2025 - 2 hours
Name …………………………………………….… Index Number………………………….
School ………………….…...…………………….. Admission No…………………………..
Date…………………………………
Instructions to Candidates
(a) Write your name and Index number in the spaces provided.
(b) Write the Name of the School and the Admission number and Date in the spaces provided.
(c) Answer all the questions in the spaces provided
(d) ALL working MUST be clearly shown where necessary
(e) Mathematical tables and electronic calculators may be used.
(f) Candidates must answer the questions in English.
FOR EXAMINER’S USE ONLY
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24 25 26 27 28
Page 1 of 15
2
1. Figure 1 shows how protons, neutrons and electrons behave differently when they
move at the same velocity in an electric field.
Figure 1.
(a) Identify the charge of the plates marked A and B in the figure. (2marks)
Charge of A…………………………………………………………………….
Charge of B……………………………………………………………………
(b) Suggest a reason why the atomic mass and the atomic number of two isotopes
of an element are not always equal. (1mark)
………………………………………………………………………………………………………
…………………………………………………………………………………………...............
2 Complete combustion of the biofuels made from the sewage sludge produces the
greenhouse gas carbon (iv) oxide.
(a) Suggest one possible environmental concern associated with combustion of these
biofuels. (1mark)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
(b) Give the name of another greenhouse gas emitted during combustion of biofuels.
…………………………………………………………………………………………. (1mark)
………………………………………………………………………………………………………..
Page 2 of 15
3
3. A patient was given the drugs with a prescription as follows
3 x 3
(a) Give the interpretation of that prescription. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) The patient decided to take the recommended number of tablets at 8.00am.
Determine the time the patient should take the next set of tablets according to the
prescription. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
4 Describe how you would prepare a 2M solution of hydrochloric acid from a 20cm3 of
12.4M hydrochloric acid in the laboratory. (2marks)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
5 (a) Write the electron configuration of Al3+ ion. (1mark)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(b) When anhydrous aluminium chloride, Al2Cl6, is added to water, a solution forms
which is strongly acidic.
(i) Suggest the pH of the solution formed when a universal indicator paper is
dipped into the solution. (1mark)
………………………………………………………………………………………………………
(ii) Identify the ion in the solution which is responsible for the acidic property of
the solution. (1mark)
……………………………………………………………………………………………………
……………………………………………………………………………………………………
Page 3 of 15
4
6 (i) On the figure 2 below, sketch a graph to show the trend in the atomic radius of
successive elements in period 3 of the periodic table. (1mark)
Figure 2
(ii) Explain your answer in (i) above. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
7 The concentration of dilute hydrochloric acid can be determined by titration using a
standard solution of barium hydroxide.
(a) Hydrochloric acid is added to the burette using a funnel. State why it is good
practice to remove the funnel from the burette before the titration. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Before the first titration, the 25ml pipette is rinsed with small volume of the same
barium hydroxide solution. Explain why this practice is important. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Page 4 of 15
5
8. Nitrogen (iv) oxide decomposes at a high temperature as shown in the chemical
system below.
2NO2 (g) 2NO (g) + O2 (g) ; ∆H = + 113kJ/mol
(a) State how decomposition of nitrogen (iv) oxide would be affected if the pressure is
increased. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) A 0.317 moles sample of nitrogen (iv) oxide is placed in a sealed flask and heated
at a constant temperature until an equilibrium is reached. Given that at
equilibrium, the flask contains 0.120 moles of oxygen gas, determine the moles
of nitrogen (iv) oxide gas at equilibrium. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
8 Figure 4 shows the bonding between oxygen and fluorine in a molecular structure.
Figure 4
(a) Label the bond shown in the structure. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Determine the oxidation state of oxygen in the molecule. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(c) Write the electron configuration of oxygen in the molecule. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Page 5 of 15
6
9 Table 1 shows some enthalpy change data. Study the table and answer the questions
that follow.
Table 1
Enthalpy change / kJmol-1
Ca2+(g) Ca2+(aq) - 1650
Cl- (g) Cl- (aq) - 364
Ca2+ (g) + 2Cl- (g) CaCl2 (s) - 2237
(a) Determine the enthalpy change that occurs when solid calcium chloride dissolves
in water. (2marks)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) How would the temperature change when calcium chloride dissolves in water?
………………………………………………………………………………………….. (1mark)
…………………………………………………………………………………………………………
10 (a) Write a chemical equation of reaction of phosphorus with excess oxygen gas to
form phosphorus (v) oxide gas. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(a) Using litmus papers, describe a test you would carry out in a test tube to
distinguish between Sodium oxide and the oxide formed in (a) above. (2marks)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Page 6 of 15
7
11 The half-equations for two electrodes that combine to make a dry cell are
Zn(s) Zn2+ (aq) + 2e- ………..Equation 1
2MNO2 (s) + 2NH4+(aq) + 2e- Mn2O3 (s) + 2NH3 (g) + H2O (l)…Equation 2
(b) Identify the oxidizing agent in this cell. (½marks)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(c) Which equation of the reaction is taking place at the cathode. (½marks)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
12 By filling in the spaces provided below, describe how a student would give the
difference between aqueous solutions of Potassium nitrate and Potassium sulphate
I. Reagent (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
II. Observation with potassium nitrate solution (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
III. Observation with potassium sulphate. (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
13. (a) Explain why metals such as magnesium and aluminium are good conductors of
electricity (1mark)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
(b) Give two reasons why aluminium is preferred to magnesium for making cooking
pans (2marks)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
Page 7 of 15
8
14. Figure 5 shows the apparatus that is used to separate a mixture of liquids K and M
using fractional distillation.
Figure 5
(a) Explain why fractional distillation is preferred to simple distillation to separate
liquids K and M. (1mark)
………………………………………………………………………………………………………
……………………………………………………………………………………………………….
(b) Suggest labels that should be added to positions T and U in the figure to show
the direction of flow of water. (1mark)
Position T……………………………………….. Position U…………………………….
15. In the extraction of metals, both carbon and carbon (ii) oxide are used as the reducing
agents .
(a) Explain why Sodium metal is not extracted using reduction method (1mark)
…………………………………………………………………………………………………………
(b) Why is carbon (ii) oxide and not carbon being referred to as the chief reducing
agent . (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Page 8 of 15
9
16. C60 forms hydrocarbons with similar chemical properties to those of alkenes. One
such hydrocarbon is C60H18.
(a) Explain why C60H18 is referred to as a hydrocarbon? (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) C60H18 is an alkene though with multiple double covalent bonds. Identify one
chemical that can be used to test for the presence of double bonds between carbon
atoms in the alkene molecules. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(c) State the observations made when the test is carried out using the chemical
identified in (b) above. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
17. Chlorine is added to some drinking water supplies to decrease the risk of people
suffering from diseases such as cholera.
(a) State why the amount of chlorine added must be controlled. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Give the chemical family name of the group in the periodic table in which
chlorine belong. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(c) Using a solution of lead (ii) nitrate, explain how the presence of chloride ions in
the drinking water can be confirmed. (2marks)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………
Page 9 of 15
10
18. Figure 6 below shows a reaction pathway. Study it and answer the questions that
follow.
Figure 6
(a) Give the name of the type of the reaction shown. Give reason for your answer.
……………………………………………………………………………………….. (2marks)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Identify the arrow which represents
I. Activation energy (½marks)
…………………………………………………………………………………………………………
II. Heat change for the reaction. (½marks)
…………………………………………………………………………………………………………
19. In the extraction of sulphur by Frasch process, water at a temperature of 1700c is
pumped into the sulphur deposits.
(a) State the role of the water. (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
(b) Explain how a temperature of 1700c is achieved. (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
Page 10 of 15
11
20. A student reacted nitric (v) acid with a base to form a solution of magnesium nitrate
(a) Write the chemical formula of the base. (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
(b) The student evaporates the water and obtained a solid magnesium nitrate. In the
space provided below, draw a labeled set up diagram which could have been used
to evaporate the solution. (2marks)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
(c) Give the name of the products formed when solid magnesium nitrate is heated
until there is no further change in mass. (1mark)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
(d) State how the thermal stability of the nitrates of group II metals change down the
group. (1mark)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
21. In terms of structure and bonding, explain why silicon (iv) oxide has a higher melting
point than carbon (iv) oxide. (2marks)
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
Page 11 of 15
12
22. (a) Complete the following nuclear equations to show the mass numbers and atomic
numbers of the emitted particles X and Y. The letters are not the actual symbols
of the particles.
Give the actual names of particles X and Y. (2marks)
Particle X……………………………………………………………………………………………
Particle Y……………………………………………………………………………………………
(b) Determine if the nuclide is stable or not. Show your working. (2marks)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
23. (a) State the kinetic theory of matter. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Explain how the decrease in volume of a fixed mass of gas affects its pressure?
…………………………………………………………………………………… (1mark)
………………………………………………………………………………………………………….
(c) Identify the gas law which gives the relationship between the volume and the
pressure of a fixed mass of gas. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Page 12 of 15
13
24. Study the flow chart below and answer the questions that follow.
(a) Identify
(i) The alkanol K……………………………………………………………….. (½marks)
(ii) The alkene L………………………………………………………………… (½marks)
(b) Give the name of the process marked A and B. (1mark)
Process A…………………………………………………………………………………………….
Process B……………………………………………………………………………………………
(c) Explain one environmental effect of usage of compound M. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
25. (a) State the difference between temporary water hardness and permanent water
hardness. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Explain why sodium and potassium salts do not cause water hardness. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(c) Explain why filtration of hard water does not remove its hardness. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
Page 13 of 15
14
26. One of the methods used in the manufacture of sodium hydroxide and chlorine is by
the use of mercury cell. The electrolyte used is a concentrated solution of sodium
chloride.
(a) The anode in the cell is made of carbon or titanium. Give reason. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
(b) Chloride (Cl-) ions and not Hydroxide (OH-) ions are preferentially discharged at
the anode. Give reason. (1mark)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(c) Explain why mercury cell is not commonly used to manufacture sodium
hydroxide and chlorine. (1mark)
…………………………………………………………………………………………………………
…………………………………………………………………………………………………………
27. When a piece of sodium is added to 200cm3 of water in a large plastic beaker, a
vigorous reaction occurs and the temperature of the water rose by 250c.
(a) Write a chemical equation of the reaction. (1mark)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
(b) Explain why it is not advisable to react a similar piece of sodium with 10cm3 of
water in a boiling tube. (1mark)
……………………………………………………………………………………………………………
……………………………………………………………………………………………………………
(c) Determine the heat change for the reaction. (2marks)
The heat capacity is 4.2 kJkg-1K-1
Page 14 of 15
15
28. Figure 7 Shows a cell used to measure the standard electrode potential of Magnesium
electrode using Hydrogen as the reference electrode.
Figure 7
(a) Identify the standard conditions for measuring the electrode potential (1mark)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(b) Identify an ionic compound that could be used in the salt bridge. (1mark)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
(c) Write the electrode potential of the standard hydrogen electrode (1mark)
.........................................................................................................................
.........................................................................................................................
(d) Water is added to the beaker containing the concentrated magnesium chloride
to form a solution. Explain the effect on the e.m.f of the cell? (1mark)
………………………………………………………………………………………………………
………………………………………………………………………………………………………
Page 15 of 15
