Question

An aluminum electrode weighing 54.98 g is used in an electrolysis reaction using a current of 1.2 A. After the reaction is stopped, the aluminum electrode weighs 54.02 g.
a. Did the aluminum electrode described above act as the cathode and the anode?

b. How many hours was the current applied to the electrolysis cell?

Answer 1

Answer:

a. Anode

b. 2.4 hours

Explanation:

a.

The initial mass of the electrode is 54.98 g and the final mass is 54.02 g. Since the mass has diminished, the electrode is acting as an anode, in which aluminum is oxidized and the aluminum cation goes into the solution.

Al(s) → Al³⁺(aq) + 3 e⁻

b.

The mass of Al that reacted is 54.98 g - 54.02 g = 0.96 g

We can establish the following relations.

• The molar mass of Al is 26.98 g/mol.
• 1 mol of Al is oxidized when 3 moles of electrons circulate.
• 1 mol of electrons has a charge of 96468 c (Faraday's constant).
• 1 A = 1 c/s
• 1 h = 3600 s

The hours during which the current was applied was:

$0.96gAl.\frac{1molAl}{26.98gAl} .\frac{3mole^{-} }{1molAl} .\frac{96468c}{1mole^{-}} .\frac{1s}{1.2c} .\frac{1h}{3600s} =2.4h$