How do u solve this chemistry electrolysis question?

2018-02-25 1:43 am

1.An electric current was passed through molten calcium chloride, producing 2g of calcium metal at the cathode.
What is the mass of chlorine produced at the anode???

2. When 2A of current are passed through a molten aluminium salt for 402 minutes. What is the mass of aluminium metal obtained at the cathode???

回答 (1)

胡雪8°

2018-02-25 2:09 am

✔ 最佳答案

1.
Molar mass of Ca = 40.1 g/mol
Molar mass of Cl₂ = 35. 5×2 g/mol = 71. 0 g/mol

Overall equation: CaCl₂(l) → Ca(s) + Cl₂(g)
Mole ratio Ca : Cl₂ = 1 : 1

No. of moles of Ca = (2 g) / (40.1 g/mol) = 0.0499 mol
No. of moles of Cl₂ = 0.0499 mol
Mass of Cl₂ = (0.0499 mol) × (71.0 g/mol) = 3.54 g

2.
Quantity of electricity passed = It = 2 × (402 × 60) C = 48240 C

1 mole of e⁻ carries 96485 C of electricity.
No. of moles of e⁻ passed = (48240 C) / (96485 C/mol) = 0.5 mol

Cathodic reaction: Al³⁺(l) + 3e⁻ → Al(l)
Mole ratio e⁻ : Al = 3 : 1
No. of moles of Al = (0.5 mol) × (1/3) = 0.5/3 mol

Molar mass of Al = 27.0 g/mol
Mass of Al obtained at the cathode = (0.5/3 mol) × (27.0 g/mol) = 4.5 g

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