Waec Chemistry 1992 Past Questions and Answers

Question 16:

• WAEC 1992

What is the change in the oxidation number of phosphorus in the the reaction represented by the following equation? 4P _(s) + 5O_(2)(g) → 2P₂O_5(g)

A. 0 to + 2
B. 0 to 5
C. +4 to + 2
D. +4 to +5
E. +4 to +7

Question 17:

• WAEC 1992

When iron rusts, it undergoes

A. Deliquescence
B. Chemical decomposition
C. Hydrolysis
D. Redox reaction
E. Combustion

Question 18:

• WAEC 1992

Consider the compounds represented by the following general formula: X₂SO₄ Y₂(SO₄)₃, 24H₂OX and Y could respectively be

A. K and AI
B. Fe and K
C. AI and Fe
D. AI and K
E. Cr and K

Question 19:

• WAEC 1992

Which of the following involves the decomposition enzymic action?

A. Esterification
B. Fermentation
C. Dehydration
D. Polymerization
E. Saponification

Question 20:

• WAEC 1992

The following salts are readily soluble in water except

A. Na₂CO₃
B. Pb(NO₃)₂
C. KCI
D. CuCO₃
E. PeSO₄