Year : 
2017
Title : 
Chemistry
Exam : 
WASSCE/WAEC MAY/JUNE

Paper 1 | Objectives

31 - 40 of 50 Questions

# Question Ans
31.

Potassium Chloride solid does not conduct electricity because

A. it is a covalent compound

B. strong cohesive forces make its ions immobile

C. strong cohesive force makes its molecule immobile

D. each of potassium and chlorine structures contain noble gas structure

Detailed Solution

For a substance to conduct electricity, it must have charge particles like electrons and ions within it that are able to move freely throughout it. In its solid state, potassium chloride (like many other ionic compounds) have fixed ions, hence, they are immobile and can't conduct electricity.
32.

When water was added to a white anhydrous substance X, the colour changed to blue. X is

A. \(CuSO_{4}\)

B. \(FeSO_{4}\)

C. \(Na_{2}SO_{4}\)

D. \(PbSO_{4}\)

Detailed Solution

When water is added to white coloured anhydrous copper sulphate, its colour changes to blue, indicating that the blue coloured copper sulphate pentahydrate is regenerated.
33.

Solubility curve can be used in the determination of the

A. amount of crystals formed

B. amount of solvent that can be recovered

C. amount of solid drugs in a given solution

D. temperature of the solution

C
34.

If 0.2g of a salt is required to saturate 200\(cm^{3}\) of water at room temperature, what is the solubility of the salt?

A. 0.2\(gdm^{-3}\)

B. 1.0\(gdm^{-3}\)

C. 2.0\(gdm^{-3}\)

D. 5.0\(gdm^{-3}\)

Detailed Solution

Solubility in \(gdm^{-3}\) = \(\frac{mass of salt in gram}{volume of liquid in dm^{3}}\)
200\(cm^{3}\) = \(\frac{200}{1000} dm^{3} = 0.2dm^{3}\)
Solubility = \(\frac{0.2g}{0.2dm^{3}}\)
= 1.0\(gdm^{-3}\)
35.

The property of a chemical reaction that is affected by the presence of a catalyst is

A. activation energy

B. free energy

C. equilibrium position

D. enthalpy change

Detailed Solution

The activation energy is the amount of energy that is required to form products in a reaction. The presence of a catalyst helps to speed up the reaction such that the energy needed for the reaction is reduced.
36.

Soluble salts can be prepared by the following methods except

A. neutralization

B. reaction of an acid with trioxocarbonate(IV) salt

C. double decomposition

D. reaction of an acid with electropositive metals

C
37.

Chemical reactions occurs when the colliding reactants have energy that is

A. less than the activation energy

B. greater than the activation energy

C. greater than the energy of the product

D. less than the energy of effective collision

Detailed Solution

The energy of the reactants must be more than the activation energy in order for product to be formed.
38.

The common feature of reactions at the anode is that

A. electrons are consumed

B. ions are reduced

C. oxidation is involved

D. the electrode dissolves

Detailed Solution

In both the electrochemical cell and the electrolytic cell, at the anode, oxidation is involved.
39.

Consider the following reaction equation: \(2NO_{(g)} + O_{{2}{(g)}} \to 2NO_{{2}{(g)}}\). What is the change in the oxidation number of nitrogen?

A. +2 to 0

B. +2 to -2

C. +2 to +4

D. +4 to +2

Detailed Solution

In NO, the oxidation number for nitrogen is N - 2 = 0
⇒ N = +2
In \(NO_{2}\), we have N - (2x2) =0
N - 4 =0
N =+4
40.

Which of the following factors characterize members of the same homologous series?

A. The chemical property change gradually throughout the series

B. physical properties of members are similar

C. They have the same molecular formular

D. Successive members undergo changes in molecular formula by \(CH_{2}\)

Detailed Solution

The difference between every successive member of the same homologous series is always \(CH_{2}\) eg methane is \(CH_{4}\) and ethane is \(C_{2}H_{6}\), difference being \(CH_{2}\).
31.

Potassium Chloride solid does not conduct electricity because

A. it is a covalent compound

B. strong cohesive forces make its ions immobile

C. strong cohesive force makes its molecule immobile

D. each of potassium and chlorine structures contain noble gas structure

Detailed Solution

For a substance to conduct electricity, it must have charge particles like electrons and ions within it that are able to move freely throughout it. In its solid state, potassium chloride (like many other ionic compounds) have fixed ions, hence, they are immobile and can't conduct electricity.
32.

When water was added to a white anhydrous substance X, the colour changed to blue. X is

A. \(CuSO_{4}\)

B. \(FeSO_{4}\)

C. \(Na_{2}SO_{4}\)

D. \(PbSO_{4}\)

Detailed Solution

When water is added to white coloured anhydrous copper sulphate, its colour changes to blue, indicating that the blue coloured copper sulphate pentahydrate is regenerated.
33.

Solubility curve can be used in the determination of the

A. amount of crystals formed

B. amount of solvent that can be recovered

C. amount of solid drugs in a given solution

D. temperature of the solution

C
34.

If 0.2g of a salt is required to saturate 200\(cm^{3}\) of water at room temperature, what is the solubility of the salt?

A. 0.2\(gdm^{-3}\)

B. 1.0\(gdm^{-3}\)

C. 2.0\(gdm^{-3}\)

D. 5.0\(gdm^{-3}\)

Detailed Solution

Solubility in \(gdm^{-3}\) = \(\frac{mass of salt in gram}{volume of liquid in dm^{3}}\)
200\(cm^{3}\) = \(\frac{200}{1000} dm^{3} = 0.2dm^{3}\)
Solubility = \(\frac{0.2g}{0.2dm^{3}}\)
= 1.0\(gdm^{-3}\)
35.

The property of a chemical reaction that is affected by the presence of a catalyst is

A. activation energy

B. free energy

C. equilibrium position

D. enthalpy change

Detailed Solution

The activation energy is the amount of energy that is required to form products in a reaction. The presence of a catalyst helps to speed up the reaction such that the energy needed for the reaction is reduced.
36.

Soluble salts can be prepared by the following methods except

A. neutralization

B. reaction of an acid with trioxocarbonate(IV) salt

C. double decomposition

D. reaction of an acid with electropositive metals

C
37.

Chemical reactions occurs when the colliding reactants have energy that is

A. less than the activation energy

B. greater than the activation energy

C. greater than the energy of the product

D. less than the energy of effective collision

Detailed Solution

The energy of the reactants must be more than the activation energy in order for product to be formed.
38.

The common feature of reactions at the anode is that

A. electrons are consumed

B. ions are reduced

C. oxidation is involved

D. the electrode dissolves

Detailed Solution

In both the electrochemical cell and the electrolytic cell, at the anode, oxidation is involved.
39.

Consider the following reaction equation: \(2NO_{(g)} + O_{{2}{(g)}} \to 2NO_{{2}{(g)}}\). What is the change in the oxidation number of nitrogen?

A. +2 to 0

B. +2 to -2

C. +2 to +4

D. +4 to +2

Detailed Solution

In NO, the oxidation number for nitrogen is N - 2 = 0
⇒ N = +2
In \(NO_{2}\), we have N - (2x2) =0
N - 4 =0
N =+4
40.

Which of the following factors characterize members of the same homologous series?

A. The chemical property change gradually throughout the series

B. physical properties of members are similar

C. They have the same molecular formular

D. Successive members undergo changes in molecular formula by \(CH_{2}\)

Detailed Solution

The difference between every successive member of the same homologous series is always \(CH_{2}\) eg methane is \(CH_{4}\) and ethane is \(C_{2}H_{6}\), difference being \(CH_{2}\).