Question

A solution of Fe₂(SO₄)₃ is electrolysed for ‘x’ min with a current of 1.5 A to deposit 0.3482 g of Fe. The value of ‘x’ is ______. (Nearest integer)

(Given, 1 F = 96500 C mol⁻¹, Atomic mass of Fe = 56)

Answer 1

A solution of Fe₂(SO₄)₃ is electrolysed for ‘x’ min with a current of 1.5 A to deposit 0.3482 g of Fe. The value of ‘x’ is 20.

Explanation:

Given: Mass of Fe deposited = 0.3482 g

Current (I) = 1.5 A

Time (t) = x min

1 F = 96500 C mol⁻¹

Atomic mass of Fe = 56

In Fe₂(SO₄)₃, iron is in the +3 oxidation state, so 3 electrons are required to deposit each Fe³⁺ ion.

Moles of Fe = `0.3482/56`

= 0.00622 mol

Each Fe³⁺ needs 3 moles of electrons:

Total charge (Q) = n × F × z

= 0.00622 × 96500 × 3

Q = 1800.69 C

We know that Q = I × t

t = `Q/I`

= `1800.69/1.5`

= 1200.46 seconds

∴ x = `1200.46/60`

x = 20 minutes