JAMB Chemistry Past Questions & Answers - Page 213

1,061.

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.

1,062.

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.

1,063.

Which of the following does NOT happen when a zinc rod is introduced into a solution of copper (ll) sulphate?

A.

Electrons flow towards the zinc rod

B.

The zinc rod dissolves

C.

The temperature of the soil changes

D.

The blue colour of the solution gradually disappears

E.

Copper metal is deposited

Correct answer is A

No explanation has been provided for this answer.

1,064.

The chemical reaction which takes place at the anode (positive electrode) in electrolysis is?

A.

oxidation

B.

hydrolysis

C.

dissociation

D.

reduction

E.

disproportionation

Correct answer is A

No explanation has been provided for this answer.

1,065.

Which of the following silver halides is readily soluble in ammonium hydroxide?

A.

Agl

B.

AgBr

C.

AgCl

D.

AgF

E.

None of the above

Correct answer is C

No explanation has been provided for this answer.