JAMB Chemistry Past Questions & Answers - Page 103

511.

MnO4(aq) + 8H + 5Fe2+ \(\to\) Mn2+(aq) + 5Fe3+(aq) + H2O. The oxidation number of maganese in the above reaction changed from

A.

+7 to +2

B.

+6 to +2

C.

+5 to +2

D.

+4 to +2

Correct answer is A

\(MnO_{{4}{(aq)}}\) has a charge of \(-1\)

Let the oxidation number of \(Mn\) in \(MnO_{{4}{(aq)}}\) be X

Recall, the oxidation number of \(O_{2}\) is \(-2\)

\(\therefore\) \(X + (-2\times 4) = -1\)

\(X - 8 = -1\)

\(X = +7\)

512.

If the relative atomic mass of an element is not a whole number, it can be deduced that the element is?

A.

Naturally radioactive

B.

abundant in nature

C.

a transition metal

D.

an isotopic mixture

Correct answer is D

No explanation has been provided for this answer.

513.

The principle of column chromatography is based on the ability of the constituents to

A.

move at different speeds in the column

B.

dissolve in each other in the column

C.

react with the solvent in the column

D.

react with each other in the column

Correct answer is A

No explanation has been provided for this answer.

514.

2SO2(g) + O2(g) \( \iff \)2SO3(g)

\( \bigtriangleup H = -395.7kJmol^{-1} \)

In the reaction above, the concentration of 2SO3(g) can be in creased by

A.

decreasing the pressure

B.

decreasing the temperature

C.

the addition of catalyst

D.

increasing the temperature

Correct answer is B

No explanation has been provided for this answer.

515.

Zn(s) + CuSO4(aq) \( \to \) ZnSO4(aq) + Cu(s)

In the reaction above, the oxidizing agent is

A.

CuSO4(aq)

B.

ZnSO4(aq)

C.

Cu(s)

D.

Zn(s)

Correct answer is A

No explanation has been provided for this answer.