How many moles of electrons are required for the reduction of :(i) 3 m

1.	How many moles of electrons are required for the reduction of :(i) 3 moles of Zn2+ to Zn, (ii) 1 mol of Cr3+ to Cr?How many Faradays of electricity will be required in each case?
Answer» (i) Given : For reduction of 3 mol Zn²⁺ to Zn; Number of moles of electrons required = ? Reduction half reaction, Zn²⁺ + 2e^- → Zn ∵ 1 mole of Zn²⁺requires 2 moles of electrons ∴ 3 moles of Zn²⁺ will require, ∵ 3 × 2 = 6 moles of electrons ∴ 1 mole of electrons = 1 F 6 moles of electrons = 6 F (ii) Given : Reduction of 1 mol of Cr³⁺ to Cr : Reduction half reaction, Cr³⁺ + 3e^-→ Cr Hence 1 mole of Cr³⁺ will require 3 moles of electrons ∵ 1 mole of electrons = 1 ∴ 3 moles of electrons = 3 F ∴ (i) 6 mol electrons and 6 Faradays. (ii) 3 mol electrons and 3 Faradays.

How many moles of electrons are required for the reduction of :(i) 3 moles of Zn2+ to Zn, (ii) 1 mol of Cr3+ to Cr?How many Faradays of electricity will be required in each case?

Answer»

(i) Given :

For reduction of 3 mol Zn²⁺ to Zn;

Number of moles of electrons required = ?

Reduction half reaction,

Zn²⁺ + 2e^- → Zn

∵ 1 mole of Zn²⁺requires 2 moles of electrons

∴ 3 moles of Zn²⁺ will require,

∵ 3 × 2 = 6 moles of electrons

∴ 1 mole of electrons = 1 F 6 moles of electrons = 6 F

(ii) Given :

Reduction of 1 mol of Cr³⁺ to Cr :

Reduction half reaction,

Cr³⁺ + 3e^-→ Cr

Hence 1 mole of Cr³⁺ will require 3 moles of electrons

∵ 1 mole of electrons = 1

∴ 3 moles of electrons = 3 F

∴ (i) 6 mol electrons and 6 Faradays.

(ii) 3 mol electrons and 3 Faradays.

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