WAEC Chemistry Past Questions & Answers - Page 116

576.

A substance L reacts with NH\(_4\)NO\(_{3(aq)}\) to generate ammonia gas. L is likely to be

A.

HCl

B.

NaOH

C.

CH3COOH

D.

CaSO4

Correct answer is B

The reaction between NH\(_4\)NO\(_{3(aq)}\) and any metal hydroxide produces ammonia, water and an alkali metal nitrate.

577.

The energy evolved when magnesium burns in air is in the form of

A.

heat

B.

heat and sound

C.

light and heat

D.

sound

Correct answer is C

When a piece of magnesium ribbon is ignited, light and heat are produced.The reaction is an exothermic reaction, as well as one that produces light energy.

578.

Which of the following gases has the lowest rate of diffusion under the same condition? [H = 1.00; He = 4. 00; O = 16.0; CI = 35.5]

A.

CI2

B.

H2

C.

He

D.

O2

Correct answer is A

According to Graham's law of diffusion and effusion,

r \(\propto\) \(\sqrt{\frac{1}{M}}\).

Therefore, the more the molar mass, the less the rate of diffusion and effusion.

579.

The postulate that molecules are in constant random motion best explains why liquids

A.

can undergo solidification

B.

maintain their volumes

C.

are incompressible

D.

have no characteristic shape

Correct answer is A

No explanation has been provided for this answer.

580.

At ordinary temperature H\(_2\)O is a liquid while H\(_2\)S is a gas. This is because H\(_2\)O has

A.

weak intermolecular forces holding its molecules together

B.

strong hydrogen bonds holding its molecules together

C.

induced dipole-induced dipole forces between its molecules

D.

ionic force between its molecules

Correct answer is B

H\(_2\)O has stronger intermolecular dipole--dipole interaction because of the greater polarity (or a hydrogen bond). Because of the stronger intermolecular interaction H\(_2\)O is more stable and exists as a liquid.