JAMB Chemistry Past Questions & Answers - Page 112

557.

Octane number is highest in petrol containing a high proportion of

A.

heptane

B.

octane

C.

2-methylpentane

D.

2, 4-dimethylpentane

E.

2,2,4-trimethylpentane

Correct answer is E

No explanation has been provided for this answer.

558.

The rate of the hydrogen in the reaction Zn(s) + 2HCI (aq) → ZnCI 2(g) + H 2(aq) + H 2(g) can be increased by

A.

using Zinc powder instead of Zinc granules

B.

using dilute instead of concentrated hydrochloric acid

C.

cooling the container in which the mixture is placed

D.

using an alloy of zinc instead of pure zinc

E.

using hydrogen chloride gas instead of hydrochloric acid solution

Correct answer is A

No explanation has been provided for this answer.

559.

Why is potassium fluoride added to the electrolyte in the extraction of sodium from fused sodium chloride?

A.

Pure sodium chloride does not conduct electricity

B.

Potassium fluoride prevents the sodium produced from attacking the electrodes

C.

Potassium fluride increases conductivity

D.

Potassium fluride reduces the temperature at which sodium chloride fuses

E.

the potassium fluride acts as a catalyst

Correct answer is D

No explanation has been provided for this answer.

560.

Locally produced soap in which wood ash is used as the base is usually soft because the wood ash contains a lot of

A.

sodium ions

B.

potassium ions

C.

lithium ions

D.

calcium ions

E.

magnesium ions

Correct answer is B

No explanation has been provided for this answer.