JAMB Chemistry Past Questions & Answers - Page 151

751.

Fluorine does not occur in the free state in nature because

A.

it is a poisonous gas

B.

it belongs to the halogen family

C.

it is inert

D.

of its high reactivity

Correct answer is D

No explanation has been provided for this answer.

752.

In a chemical reaction, the change in concentration of a reactant with time is

A.

entropy of reaction

B.

enthalpy of reaction

C.

rate of reaction

D.

order of reaction

Correct answer is C

No explanation has been provided for this answer.

753.

In an equilibrium reaction, which of the following conditions indicates that maximum yield of the product will be obtained?

A.

Equilibrium constant is very large

B.

∆H - T∆S = O

C.

∆ H > T ∆ S

D.

Equilibrium constant is less than zero

Correct answer is A

No explanation has been provided for this answer.

754.

If the change in free energy of a system is -899 Jmol-1 and the entropy change is 10Jmol-1k-1 at 250C, calculate the enthalpy change.

A.

+2081 Jmol-1

B.

-2081 Jmol-1

C.

-649 Jmol-1

D.

+649 Jmol-1

Correct answer is A

∆G = ∆H - T∆S
-899 = ∆H - 2980
∆H = -899 + 2980 = + 2081 Jmol-1

755.

How many faraday of electricity is required to produce 0.25 mole of copper?

A.

1.00F

B.

0.01F

C.

0.05F

D.

0.50F

Correct answer is D

Cu → Cu2+ + 2e
1mole Cu requires 2f
0.25 mole Cu requires x
x = 0.25x2/1 = 0.50f