JAMB Chemistry Past Questions & Answers - Page 298

1,486.

Calculate the mass, in kilograms, of magnesium produced by the electrolysis of magnesium (II) chloride in a cell operating for 24 hours at 500 amperes.

2.7

5.4

10.8

21.7

View answer & explanation

Correct answer is B

Mg + 2e → 24 gms
2f → 24 gms
2 x 96,500 → 24 gms
Q = (500 x 1440 x 60)
Q = 4320000 C
1 mole of mg = (1) / (2 x 96,500) x (43200000) / (1)
= (24)/(1) = (1036800000) / (193000) = 5372.020725 gms
in leg = (5372.020725) / (1000) = 5.4 leg

1,487.

Copper (II) tetraoxosulphate (VI) solution is electrolyzed using carbon electrodes. Which of the following are produced at the anode and cathode respectively ?

Copper and oxygen

Oxygen and copper

Hydrogen and copper

Copper and hydrogen

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

1,488.

How many grams of H₂SO₄ are necessary for the preparation of 0.175 dm³ of M 6.00 M H₂SO₄?

(S = 32.06, O = 16.00 H = 1.00)

206.0 g

103.0 g

98.1 g

51.5 g

View answer & explanation

Correct answer is B

1 mole of H₂SO₄ ≈ 98 gms
0.175 dm³ of 6.0 m H₂SO₄
1000 cm³ ≈ dm³
(0.175) / (1000) of 6.0 m H₂SO₄
0.000175 x 6 x 98 ≈ 0.1029 gms
1 dm³ - 1000 cm³
∴ 0.1029 x 1000 = 103 gms