WAEC Chemistry Past Questions & Answers - Page 97

481.

The oxide from electric power station is

A.

carbon (IV) oxide

B.

copper (ll) oxide

C.

nitrogen (IV) oxide

D.

sulphur (IV) oxide

Correct answer is C

 Nitric oxide is an important component of the air pollution generated by automotive engines and thermal power-generating plants.

sulphur dioxide may also be produced in case of fuel containing sulphur, Nigeria crude is sulphur free,

482.

The most common process in the extraction of metals from their ore is

A.

catalysis

B.

electrolysis

C.

oxidation

D.

reduction

Correct answer is D

No explanation has been provided for this answer.

483.

Which of the following gases is used to retard the vaporization of the filament in a light bulb?

A.

Argon

B.

Helium

C.

Hydrogen

D.

Oxygen

Correct answer is A

No explanation has been provided for this answer.

484.

The purity of a solid sample can best be determined by its?

A.

boiling point

B.

melting point

C.

conductivity

D.

solubility

Correct answer is B

- The presence of impurities in a substance results in a lower melting point due to a process called melting point depression.

- That implies a pure solid has a SHARP melting point which is of the standard value when compared.

485.

The production of biogas from the fermentation of waste materials is an example of

A.

combustion

B.

incineration

C.

refining

D.

recycling

Correct answer is D

No explanation has been provided for this answer.