JAMB Past Questions and Answers - Page 1687

8,431.

Magnesium (IV) oxide is known to hasten the decomposition of hydrogen peroxide. Its main action is to?

A.

increase the surface area of the reactants

B.

increase the concntration of the reactants

C.

lower the activation energy for the reactio

D.

lower the heat of reaction, ∆H, for the reaction

Correct answer is C

As a catalyst, MnO2 lowers activation energy of a reaction.

8,432.

2H2S(g) + SO2(g) → 3S(s) + 2H2O(I). The above reaction is?

A.

a redox reaction H2S is the oxidant and SO2 is the reductant

B.

a redox reaction in which SO2 is the oxidant and H2S is the reductant

C.

not a redox reaction because there is no oxidant in reaction equation

D.

not a redox because there is no reductant in the reaction equation

Correct answer is B

In the above reaction, H\(_2\)S is oxidized to H\(_2\)O while SO\(_2\) is reduced to S. Hence, H\(_2\)S is the reductant while SO\(_2\) is the oxidant.

8,433.

MnO-4 + 8H+ + ne → Mn++ + 4H2O. Which is the value of n in the reaction above?

A.

2

B.

3

C.

4

D.

5

Correct answer is D

MnO-4 + 8H+ + ne- → Mn++ + 4H2O

Since Mn has 7 electrons on one side and 2 electrons on the other side. The value of ne- is 5.

8,434.

Which of the following equimolar solutions, Na2CO3 Na2 SO
4CI FeCI3 CH3COONa,
have pH greater than 7?

A.

FeCI 3 and NH 4CI

B.

Na2CO3, CH3COONa and Na,Na2SO4

C.

Na2CO3 and CH3COONa

D.

FeCI3, CH3COONa and NH4CI

Correct answer is C

No explanation has been provided for this answer.

8,435.

If a current of 1.5 A is passed for 4.00 hours through a molten tin salt and 13.3g of tin is deposited, what is the oxidation state of the metal in the salt?

(Sn = 118.7, F = 96500 C mol-1)

A.

1

B.

2

C.

3

D.

4

Correct answer is B

Q = It = 1.5 x 4 x 60 x 60
13.3 g = 216000 C
118.7 g = (216000 x118.7) / (13.3) = 1927759.4 C
06500 C - 1 mole
1927759.4 C = (1927759.4) / (96500) = 1.998 = 2