WAEC Chemistry Past Questions & Answers - Page 125

621.

Which of the following metals could be used as sacrifical anode for preventing the corrosion of iron?

A.

Copper

B.

Lead

C.

Magnesium

D.

Silver

Correct answer is C

No explanation has been provided for this answer.

622.

What mass of copper would be formed when a current of 10.0 A is passed through a solution of CuSO4 for 1 hour? [Cu = 63.5; 1F = 96500C]

A.

5.9 g

B.

11.8 g

C.

23.8 g

D.

47.3 g

Correct answer is B

No explanation has been provided for this answer.

623.

What is the value of n in the following equation? Cr2O72- + 14H+ + ne- → 2Cr 3+ + 7H2O

A.

2

B.

3

C.

6

D.

7

Correct answer is C

No explanation has been provided for this answer.

624.

Consider the following reaction equation: X(g)
+ Y(g) ⇌ XY(g); ∆H = + 220KJ mol-1 If the temperature of the system is increased, the

A.

backward reaction would be favoured

B.

forward reaction would favoured

C.

reaction would stop

D.

reaction would be at equilibrium

Correct answer is B

No explanation has been provided for this answer.

625.

On evaporation to dryness, 250 cm3 of saturated solution of salt X with relative molar mass 101 gave 50.5g of the. What is the soluility of the salt?

A.

1.0 mol dm-3

B.

2.0 mol dm-3

C.

4.0 moldm-3

D.

5.0 moldm-3

Correct answer is B

50.5g 0f salt X is contained in 250cm3,

what mass of X is contained in 1000cm3 

= (50.5 x 1000) ÷ 250 = 202g

no of moles of salt x = mass÷ molar mass

= 202÷ 101 = 2.0mol/dm3