Question

A certain quantity of electricity is passed through aqueous Al₂(SO₄)₃ and CuSO₄ solutions connected in series. 0.09 g of Al is deposited on cathode during electrolysis. The amount of copper deposited on cathode in grams is:

(Atomic mass of Al = 27 u, Cu = 63.5 u)

विकल्प

• 0.318

• 31.8

• 0.636

• 3.18

Answer 1

0.318

Explanation:

Aluminium sulphate: Al₂(SO₄)₃

\[\ce{Al^3+ + 3e^- -> Al}\]

(mole ratio)₁ = `("moles of product")/("moles of e"^-) = 1/3`

Copper sulphate: CuSO₄ 

\[\ce{Cu^2+ + 2e^- -> Cu}\]

(mole ratio)₂ = `("moles of product")/("moles of e"^-) = 1/2`

`"W"_1/(("mole ratio")_1 xx "M"_1) = "W"_2/(("mole ratio")_2 xx "M"_2)`

`0.09/(1/3 xx 27) = "W"_2/(1/2 xx 63.5)`

W₂ = `0.09/2 xx 3/27 xx 63.5` = 0.3175 g ≈ 0.318 g