WAEC Past Questions and Answers - Page 1611

8,051.

Consider the following equation; Cr2O7(aq)2- + 14H+(aq) + 6e- → 2Cr3+(aq) + 7H2O(I). 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.

8,052.

A visible change is observed when a strip of iron is placed in an aqueous solution of

A.

FeSO4

B.

ZnSO4

C.

CuSO4

D.

MgSO4

Correct answer is C

No explanation has been provided for this answer.

8,053.

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

A.

Cu(NO 3 )2

B.

AgNO3

C.

K2CO3

D.

CaCO3

Correct answer is B

No explanation has been provided for this answer.

8,054.

CuSO4 5H2O 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.

8,055.

Equal amounts of marble chips are reacted separately with 100cm3 of hydrochloric acid of different concentrations . if all the marble chips reacted, which of the following remained the same in each case?

A.

Average rate of evolution of gas

B.

Total mass of gas evolved during the reaction

C.

Time taken for the reaction to reach completion

D.

lnitial reaction rates

Correct answer is B

No explanation has been provided for this answer.