Question

An aqueous solution of calcium hydroxide is electrolysed using carbon electrodes.

1) what will be liberated at the anode?
2) It was observed that during the electrolysis, the mass of the anode decreased and a white precipitate was formed. Explain.
Thanks :)

Answer 1

1) Oxygen will be liberated at anode

2) White precipitate is due to the formation of calcium carbonate CaCO3

Step-by-step explanation:

1) The reactions at the anode and cathode involving the electrolysis of Ca(OH)2 are:

Cathode (reduction):

`Ca^(2+)+2e^(-)\rightarrow 2Ca`

Anode (oxidation):

`4OH^(-)(aq)\rightarrow 2H_(2)O(l)+O_(2)(g)+4e^(-)`

Thus oxygen gas will be liberated at anode

2) At the anode the O₂ gas reacts with the carbon (C) electrode to form CO₂ which then reacts with Ca(OH)₂ to form a white precipitate of CaCO₃.

Answer 2

In the anode, the oxygen in the hydroxide ion will be oxidized produced oxygen gas. This gas will be liberated in the anode.
The mass of the anode will decrease because the Carbon in the electron reacts with Calcium to form Calcium carbonate which is the white precipitate.