WAEC Chemistry Past Questions & Answers - Page 67

331.

In which of the following compounds does hydrogen form ionic compounds?

A.

CH\(_{4}\)

B.

HCl

C.

NH\(_{3}\)

D.

NaH

Correct answer is D

The bonding between a non-metal and a metal is an ionic bonding. In metal hydrides, Hydrogen takes on the ionic charge of -1, hence forming an ionic bond with the metals.

332.

A reaction is endothermic if the

A.

reaction vessel feels cool during the reaction

B.

enthalpy change is negative

C.

bond forming energy exceeds bond breaking energy

D.

heat of formation of reactants exceeds heat of formation of products

Correct answer is A

Endothermic reactions absorb heat from their surroundings during the reaction process. This means that in the course of the reaction the vessel being used in the reaction will be cool in the process.

333.

An acidic salt has

A.

double anions in its aqueous solution

B.

a single cation in its aqueous solution

C.

hydrogen ions in its aqueous solution

D.

hydrogen atoms in its aqueous solution

Correct answer is C

Acid salts are salts whose aqueous solutions are acidic in character, implying that their aqueous solutions possess hydrogen ions.

334.

What is the solubility of a salt if 0.4g of it is obtained on evaporating 200\(cm^{3}\) of its saturated solution to dryness?

A.

0.08\(gdm^{-3}\)

B.

2.00\(gdm^{-3}\)

C.

8.00\(gdm^{-3}\)

D.

80.00\(gdm^{-3}\)

Correct answer is B

1000\(cm^{3}\) = 1\(dm^{3}\)

200\(cm^{3}\) = 0.2\(dm^{3}\)

⇒ 0.2\(dm^{3}\) contains 0.4g

hence, solubility of the salt which is the amount of the salt dissolvable in 1\(dm^{3}\) is

\(\frac{0.4g}{0.2dm^{3}} = 2.0gdm^{-3}\)

335.

The process of extraction of iron from its ore is

A.

decomposition

B.

oxidation

C.

reduction

D.

sublimation

Correct answer is C

The Iron is to to be gotten by the removal of oxygen from its ore, and this is called a reduction reaction.