Chemistry Paper 2 WASSCE (PRIVATE CANDIDATE) 2019

Question 1

What is an ion?
[2 marks]

State the role of each of the following substances in the treatment of river water for town supply:
1. sand bed.
2. chlorine.
3. alum
  [2 marks]
The collision theory suggests that for two particles to react, they collide. What two factors whether or not the collision would lead to formation of products? [2 marks]

Explain why palm wine tastes sour after some days.
[2 marks]

List two chemical properties of acids.
[2 marks]

The following reaction occurs when a piece of iron is exposed to moist air. For some days:
4Fe_(s) + 3O₂_(g) + χH2O_(i) → 2Fe2O₃ _χ H₂O_(s).

State two methods by which this reaction could be prevented.
[2 marks]

Consider the following elements:

Li, Be, B, N, O, F.

State, giving reasons:
1. which elements has the smallest second ionization energy
2. one pair of elements which can form an ionic bond.
A mole of an ideal gas occupies 22.4dm³ at 273. 15 k and a pressure of 1.0132 × 10⁵ N m^-2. Determine the gas constant R.

[2 marks]

State one way to reduce the environmental problems brought about by industrialization.
[2 marks]

For each of the following compounds, write the structure of an isomeric compound which satisfies the indicated property:

CH₃CH₂CH₂CH₂OH, an isomeric alkanol which is not oxidized by acidified KMnO₄:

CH₃COOCH₃, an isomeric compound which gives effervescence with aqueous NaHCO₃.

Observation

This question was compulsory for all candidates. However, their performance in it was average as majority of them displayed poor knowledge of most of the chemical terms in the questions.

In part (a) majority of the candidates could not satisfactorily explain the term ion.

In part (b) majority of the candidates were able to state the roles of the substances in the treatment of river water for town water supply.

In part (c) majority of the candidates did not understand collision theory.

In part (d) majority of the candidates could not satisfactorily explain why palm wine tastes sour after some days.

In part (e) majority of the candidates were familiar with the chemical properties of acids.

In par (f) majority of the candidates stated the methods of preventing rusting correctly.

In part (g) majority of the candidates displayed poor knowledge of second ionization energy and ionic bond formation.

In part (h) majority of the candidates could not apply the ideal gas equation in determining gas constant R.

In part (i) majority of the candidates stated ways of reducing the environmental problems brought about by industrialization.

In part (j) majority of the candidates could not write the isomeric compound for the given organic compound.

The expected answers include:

An ion is a charged particle formed from an atom or group of atoms by loss or gain of electron(s)

1. for filtration
2. for killing bacteria / for sterilizing the water
3. for coagulation /agglomeration / flocculation of suspended particles
- energy of collision / colliding particles/possession of minimum amount of energy/activation energy
- alignment of the particles / correct orientation
It has been oxidized to ethanoic acid by bacteria / atmospheric oxygen.

- neutralize bases to form salts
- acids react with electropositive metals to liberate hydrogen
- reacts with trioxosulphate (IV) salts to liberate SO_2(g).
- reacts with trioxocarbonate (IV) salts to liberate CO_2(g)
- turns blue litmus paper red
- galvanizing
- electroplating
- cathodic protection / anodic sacrificing
- greasing /oiling
- painting
1. Be because it forms the most stable 2⁺ state.

- using alternative energy sources
- improving operational practices
- public education
- enforcing legislation and regulation on waste management
1. (CH₃)₃ COH
2. CH₃CH₂CH₂CH₂CH₃/(CH₃)₂CHCH₂CH₃
3. CH₃CH₂ COOH

Chemistry Paper 2 WASSCE (PRIVATE CANDIDATE), 2019

Question 1

Observation