JAMB Past Questions and Answers - Page 1568

7,836.

If one of the following oxides is heated with hydrogen or carbon using a bunsen burner, it is not reduced to the metal. Which one is it?

A.

Lead oxide

B.

Magnesium oxide

C.

Copper oxide

D.

Tin oxide

E.

Iron oxide

Correct answer is B

No explanation has been provided for this answer.

7,837.

Cellulose and starches can be classified as one of the following?

A.

sugars

B.

sucrose

C.

hydrocarbons

D.

carbohydrates

E.

isomers

Correct answer is D

No explanation has been provided for this answer.

7,838.

The best way of collecting chlorine is?

A.

by downward displacement of air

B.

by upward displacement of air

C.

over water

D.

under water

E.

over mercury

Correct answer is B

Chlorine gas is 2.5 times denser than air, hence it is best collected by the downward delivery or upward displacement of air.

7,839.

A cold aqueous solution of sodium chloride is electrolyzed using a graphite anode and an iron cathode. In the course of the electrolysis the electrolyte is continuously stirred. The liquid left after electrolysis will therefore consist of?

A.

sodium hydroxide solution

B.

chlorine water

C.

pure water

D.

sodium hypochlorite solution

E.

hydrochloric acid solution

Correct answer is A

we take cold aqueous to be concentrated solution of NaCl.

NaCl → \(Na^+    + Cl^-\)

 \(H_2O → H^+   + OH^-\)

H ion will be preferably discharged at the cathode while Cl ion will be discharged at the anode(due to high concentration)

Thus, NaOH is left in the solution.

7,840.

Hardening of an oil may be achieved by?

A.

boiling the oil with water

B.

boiling the oil with a catalyst

C.

treating the oil with sodium hydroxide

D.

treating the oil with hydrogen and catalyst

E.

distilling oil under reduced pressure

Correct answer is D

No explanation has been provided for this answer.