Chemistry questions and answers

Chemistry Questions and Answers

Learn more about the properties, composition, and structure of substances (elements and compounds) with these Chemistry questions and answers. This Test can be used by students preparing for Chemistry in JAMB, WAEC, NECO or Post UTME.

1,206.

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.

1,207.

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.

1,208.

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.

1,209.

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.

1,210.

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 evoluton of gas

B.

Total mass of gas evolved during the reaction

C.

Time taken for the reaction to reach completion

D.

Initial reaction rates

Correct answer is B

The total mass of gas evolved during the reaction will remain the same in each case. This is because the amount of marble chips is the same in each case, and the reaction goes to completion. Therefore, the same amount of gas will be produced in each case, regardless of the concentration of the hydrochloric acid.