Cameroon GCE advanced level June 2025 chemistry 2
Cameroon GCE advanced level June 2025 chemistry 2
SECTION A: PHYSICAL AND GENERAL CHEMISTRY
1 . (a) What is a redox reaction?
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( lmark)
(b) 31.0 cm3 of an acidified KjMn04 solution was required to completely oxidize 50 cm3 of 0.25 M
solution of oxalic acid (H2C204). The unbalanced ionic equation is:
Mn
(a+q
^ 2®4(aq) + Mn04(aq) + H+ ) + C02(g) + H20(1)
(i) Write down the half equation for
A: Oxidation:
B: Reduction:
(ii) Write down the overall balanced equation
(iii ) Calculate the concentration of the KMn04 solution.
(5 murks)
(c) Bond energy can provide information about the energy changes that accompany a chemical reaction.
(i) What do you understand by the term bond energy?
(iii) Explain why most of the alpha particles went through undeflected?
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(3 marks)
(b) The half-life of tritium, a radioactive isotope of hydrogen is 12.25 years. Beginning with a 2.5 g sample
of tritium, what mass will be left after 45 years?
(c) The Collision Theory of Reaction Kinetics was developed from the kinetic theory of gases.
.. – *’ H
(i) State two postulates of the Collision Theory.
(ii)Ilydrogen peroxide decomposes according to the equation:
21hOifjiqV — 21120(1) + 02(g).
State and explain one method by which the rate of the reaction can be measured
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(iii) Given that the rate law for the reaction is Rate =K[H202]2. What does K represent > ;.
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(5 marks)
(d) Complete (he table below by filling in the missing information
Species involved Example of compound with the
type of bond
Bond type
Ionic bond
Covalent
Dative covalent bond
(3 marks)
(c) Suggest an explanation for the trigonal pyramidal shape ofNHj.
(0 Two pure liquids A and B, have vapour pressures of 1.5 x lO^ Nm‘2 and 3.5 x lO^ Nm‘2 respectively al 2()°C. If a
mixture ol the two liquids is prepared by adding 2.5 moles of A and 1.5 moles of B at the same temperature,
calculate:
(i) The partial vapour pressure of A and B in the mixture:
(ii) The total vapour pressure of the mixture.
(3 marks)
(g) A solution made up of 0.15 mol/dm3 propanoic acid (Ka = 1.35 x 10‘5 mol/dm3) and 0.35 mol/din3 sodium
propanoale, constitutes a buffer solution.
(i) What is a buffer solution?
(ii) Calculate the pH of the solution.
(2 marks)
(Total = 20 marks)
SECTION B: INORGANIC CHEMISTRY
3. (a) The elements of period three of the periodic table are; sodium, magnesium, Aluminium, silicon,
Phosphorus, Sulphur, chlorine and Argon.
(i) Sketch a graph to show the variation of Atomic Radius against atomic number for the elements.
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