WAEC Chemistry Past Questions & Answers - Page 38

186.

Which of the following substances is an example of a fine chemical?

A.

Sodium hydroxide

B.

Hydrochloric acid

C.

Ethylene

D.

Ammonia

Correct answer is B

- Fine chemicals are complex, single, pure chemical substances, produced in limited quantities.

- Heavy chemicals are produced and handled in large lots and are often in a crude state.

-  Some examples of heavy chemicals are ammonia, sulfuric acid, and sodium hydroxide.

187.

Kipps  apparatus can be used to prepare?

A.

H\(_2\)

B.

NH\(_3\)

C.

O\(_2\)

D.

H\(_2\)S

Correct answer is D

Kipp's apparatus is a laboratory apparatus specially designed for producing small amount of gases and is used to produce usually hydrogen sulfide.

188.

The group to which elements belong in the periodic table is determined by the number?

A.

electrons

B.

core electrons

C.

valence shells

D.

valence electrons

Correct answer is D

This periodic table shows the valences of element groups. 

189.

Which of the following methods is NOT used  for the separation of mixtures?

A.

Chromatography

B.

Crystallization

C.

Distillation

D.

Electrolysis

Correct answer is D

Uses of electrolysis:

  • Electrolysis is used in the extraction of metals from their ores.
  • It is used for refining certain metals such as copper and zinc.
  • Electrolysis is used for the manufacture of chlorine. 
  • Electrolysis is used for electroplating many things we use every day.

190.

The method used to collect gas in the laboratory depends on its?

I. boiling point  II. density  III. smell  IV. solubility in water

A.

i and ii only

B.

ii and iv only

C.

iii and iv

D.

i, ii, iii and iv

Correct answer is B

The method of collecting a gas produced by a chemical reaction will depend on its solubility and its density.