Calculate quantity of materials produced from the electrolysis of a molten salt.
ID: 517663 • Letter: C
Question
Calculate quantity of materials produced from the electrolysis of a molten salt. A current of 16.5A is passed through an electrolysis cell containing molten MgCl_2 for 13.3 minutes. (a) Predict the products of the electrolysis and write the reactions occurring at the anode and cathode. Write electrons as e^- Use smallest integer coefficients possible and omit states. If a box is not needed, leave it blank. Cathode reaction: Anode reaction: (b) Calculate the grams of metal or liters of gas formed at the cathode and anode (assume gases are at 298 K and 1.00 atm). Formed at cathode: Formed at anode:Explanation / Answer
(a)
Cathode reaction: (Reduction Half reaction:
Mg2+ + 2 e ------------> Mg (s)
Anode Reaction: (Oxidation Half Reaction)
2 Cl- -------------> Cl2 (g) + 2 e
(b)
According Faraday's first law of electrolysis,
At cathode,
W = M c t / Z F
W = 24 * 16.5 * 13.3 * 60 / ( 2 * 96500 )
W = Mass of Mg deposited at cathode = 1.64 g.
At anode,
W = 71 * 16.5 * 13.3 * 60 / ( 2 * 96500 )
W = mass of Chlorine gas liberated at anode = 4.84 g.
Moles of Chlorine gas liberated = mass / molar mass = 4.84 / 71 = 0.0682 mol
Assuming ideal behavior for Cl2 gas,
ideal gas equation, P V = n R T
V = 0.0682 * 0.0821 * 298 / 1.00
V = 1.67 L of Cl2 gas is liberated.
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