How many electrons must be added to the half-reaction to balance the charge after the mass has been balanced?

Question

CN ^- (aq) → CNO^- (s)
Options:

1 on the left side

1 on the right side

2 on the left side

2 on the right side

no electrons are needed

Answer 1

To balance the charge in the half-reaction, we need to determine the change in oxidation states for each element.

In this case, the oxidation state of carbon (C) in CN^- is -2 and the oxidation state of carbon in CNO^- is +4. This means that the carbon atom has gained 6 electrons.

To balance this change in oxidation states, we need to add 6 electrons to the left side of the half-reaction:

6e^- + CN^- (aq) → CNO^- (s)

Therefore, the answer is 6 electrons on the left side. None of the options given are correct.