JAMB Chemistry Past Questions & Answers - Page 160

796.

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.

797.

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.

798.

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

799.

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

800.

Calculate the quantity of electricity in coulombs required to liberate 10g of copper from a copper compound

[Cu=64, F = 96500 Cmol-1]

A.

32395.5

B.

30156.3

C.

60784.5

D.

15196.5

Correct answer is B

Cu → Cu2++ 2e
64g Cu requires 2 x 96500 coloumbs 10g Cu requires x columbs
x = 10x2x96500/64 =30156.3