Chem9

Question 1

State Faraday’s 1st Law mathematically.

Answer 1

Mass ∝ Q (or m = (M×I×t)/(Z×96,500)).

Question 2

In an experiment, 2A for 1 hr deposits 2.4 g Mg. Find eq. mass (Z = 2).

Answer 2

Q = 2A × 3600s = 7200 C; Eq.mass = (2.4 g × 96,500)/7200 = 12.15 g/eq (matches Mg²⁺).

Question 3

Graphite anode mass loss if 0.5 mol O₂ forms.

Answer 3

2C + O₂ → 2CO; 0.5 mol O₂ reacts with 12 g C → 12 g loss.

Question 4

Why use series circuits in Faraday’s 2nd Law experiments?

Answer 4

Ensures identical current (Q) passes through all electrolytes.

Question 5

Convert 2.5 F to coulombs.

Answer 5

2.5 × 96,500 = 241,250 C.

Question 6

If 3 F deposits 27 g Al, what’s Al’s eq. mass?

Answer 6

27 g/3 F = 9 g/eq (matches Al³⁺).

Question 7

Charge needed to deposit 1 g H₂ (Z = 1)?

Answer 7

Eq.mass H₂ = 1 g → 1 F = 96,500 C.

Question 8

Why is Ag used to define the coulomb (1 C = 1.118 mg Ag)?

Answer 8

Ag⁺ + e⁻ → Ag has simple 1:1 stoichiometry; precise measurements.

Question 9

Current efficiency if 8 g O₂ forms instead of theoretical 16 g.

Answer 9

Efficiency = (8/16) × 100 = 50%.

Question 10

Time to deposit 63.5 g Cu with 10 A (Z = 2).

Answer 10

2 F = 193,000 C; t = Q/I = 19,300 s (~5.36 hrs).

Question 11

Mass ratio of Fe²⁺:Fe³⁺ deposited by same Q.

Answer 11

Eq.mass ratio = 56/2 : 56/3 = 3:2.

Question 12

Why does Fe have multiple eq. masses?

Answer 12

Different oxidation states (Fe²⁺, Fe³⁺) change Z.