Question 8
- Potassium , hydrogen gas and potassium hydride exhibit different types of bonds.
Copy and complete the following table
Substance |
Type of Bonding |
Units which make-up this substance |
K |
|
|
H2 |
|
|
KH |
|
|
- (i) Arrange the following compounds in order of increasing boiling points:
H2O, CH4, H2S.
(ii) Give reasons for your answer in 8(b)(i).
(c) (i) State two processes where the concept of oxidation number is applied.
(ii) Write the formula of the oxide in which nitrogen exhibits an oxidation number of:
- +1;
- +2;
- +3.
(iii) Differentiate between a drying agent and a dehydrating agent.
Give an example of each agent.
(d) (i) State two chemical properties of an acid.
(ii) Classify each of the following solutions as acidic, basic or neutral;
- NH4Cl(aq);
- K2CO3(aq);
- Na2SO3(aq);
- CH3COONa(aq).
A fair attempt was made on this question. Majority of the candidates could not answer (a) part of the question especially the unit which make up the substance.
In (b), only few candidates could arrange the compounds in order of increasing boiling point.
In (c), candidates gave a fair attempt of application of oxidation number and also wrote formulae of compounds in which nitrogen exhibits oxidation number of +1, +2 and +3. Many candidates could not effectively differentiate between a drying agent and a dehydrating agent.
In (d), majority of the candidates that attempted the question correctly gave properties of an acid and they were also able to classify the following solutions NH4 C(aq), K2 CO3(aq);
Na2SO4(aq) and CH3COONa(aq) as either acidic, basic or neutral.