JAMB Chemistry Past Questions & Answers - Page 67

331.

In the laboratory preparation of oxygen, the gas cannot be collected by downward displacement of air because

A.

the density of oxygen is greater than that of air

B.

the density of air is nearly the same as that of oxygen

C.

oxygen is a component of air

D.

air is an impure substance

Correct answer is B

Oxygen is collected in downward displacement of water because:-

  1. Oxygen is only slightly soluble in water. Therefore, it can be collected over water without the fear of excessive dilution.
  2. Oxygen is slightly heavier than air, so it cannot be collected over air.

332.

When air which contains the gases Oxygen, nitrogen, carbondioxide, water vapour and the rare gases, is passed through alkaline pyrogallol and then over quicklime, the only gases left are;

A.

nitrogen and carbondioxide

B.

the rare gases

C.

nitrogen and oxygen

D.

nitrogen and the rare gases

Correct answer is D

The quick-lime is a drying agent that can dry most gases except ammonia. Hence it removes the water vapour. Quick-lime which is calcium oxide reacts with the carbon dioxide forming calcium carbonate. Hence carbon dioxide and monoxide is eliminated leaving nitrogen, and the rare gases

333.

A balanced chemical equation obeys the law of

A.

conservation of mass

B.

definite proportions

C.

multiple proportions

D.

conservation of energy

Correct answer is A

No explanation has been provided for this answer.

334.

Which of the following are mixtures? 
I. Petroleum 
II. Rubber latex 
III. Vulcanizer's solution 
IV. Carbon sulphide

A.

I, II and III

B.

I, II and IV

C.

I and II only

D.

I and IV

Correct answer is A

No explanation has been provided for this answer.

335.

The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence of

A.

carbon(IV)oxide

B.

carbon(ll)oxide

C.

soda

D.

glucose

Correct answer is A

No explanation has been provided for this answer.