WAEC Chemistry Past Questions & Answers - Page 134

666.

What is the change in oxidation number of manganes in the reaction represented by the following equation? MnO-4(aq) + 8H+(aq) + 5e- → Mn2+(aq) + 4H2O(l)

A.

+3 to + 2

B.

+ 4 to + 2

C.

+ 5 to + 2

D.

+ 7 to 2

Correct answer is D

No explanation has been provided for this answer.

667.

Which of the following statements about the electrolysis of CuSO4(aq) using copper cathode and platinum anode is not correct?

A.

Copper is deposited at the cathode

B.

Oxygen is liberated at the anode

C.

it is used for the purification of copper

D.

The solution becomes acidic

Correct answer is C

For purifying impure copper, the anode electrode is impure copper while the cathode electrode is pure copper, but for this question, two different electrodes were used, hence option C is the correct option to this question.

668.

Which of the following statements about the cell notation Mg/Mg2+//Cu2+/Cu is correct?

A.

copper is the anode

B.

Manesium is reduced

C.

Magnesium is the anode

D.

The double line represents the electrodes

Correct answer is B

No explanation has been provided for this answer.

669.

The rate of chemical reaction of solids are not affected by

A.

catalyst

B.

pressure

C.

particle size

D.

temperature

Correct answer is B

No explanation has been provided for this answer.

670.

Consider the equilibrium reaction represented by the following equation: 2SO2(g) + O2(g) ⇌ 2SO3(g); ∆H = 395.7 kJmol-1 Which of the following statements about the equilibrium system is correct?

A.

Addition of catalyst changes the equailibrium position

B.

Decrease in pressure increase in temperature SO3

C.

Decrease in pressure increases the equilibrium concentration of O2

D.

Increase in temperatur favours the forward reaction

Correct answer is C

No explanation has been provided for this answer.