WAEC Chemistry Past Questions & Answers - Page 93

461.

When alkynes are hydrogenated completely they produce compounds with the general molecular formula

A.

CnHn

B.

CnH2n

C.

CnH2n+2

D.

CnH2n-2

Correct answer is C

No explanation has been provided for this answer.

462.

When concentrated sodium chloride solution is electrolysed using inert electrodes, the products are

A.

oxygen and hydrogen

B.

hydrogen and chlorine

C.

sodium and oxygen

D.

sodium and chlorine

Correct answer is B

No explanation has been provided for this answer.

463.

Consider the following equation: Cr2O2-7(aq) + 14H+(aq) + 6e- → 2Cr3+(ag) + 7H2O(1). The oxidation number of chromium changes from

A.

-2 to + 3

B.

-2 to + 6

C.

+6 to +3

D.

+7 to + 6

Correct answer is C

No explanation has been provided for this answer.

464.

Which of the following compounds will leave a metal residue when heated?

A.

Cu(NO3)2

B.

AgNO3

C.

K2CO3

D.

CaCO3

Correct answer is B

No explanation has been provided for this answer.

465.

CuSO45H2O can be obtained from an aqueous solution of copper (ll) tetraoxosulphate (VI) by

A.

evaporation to dryness

B.

using chromatography

C.

precipitation

D.

crystallization

Correct answer is D

No explanation has been provided for this answer.