What is added to balance hydrogen and oxygen atoms in an oxidation reduction reaction in acidic solution?

Water for oxygen and protons for hydrogen.

Explanation:

To balance O and H in acidic medium:-

To balance Oxygen:

Add water () where there are less number of oxygen atoms. The number of the water molecules added should be equal to the number of the oxygen atoms short on either side of the reaction.

To balance Hydrogen:

Add Protons ()  where there are less number of hydrogen atoms. The number of the Protons added should be equal to the number of the hydrogen atoms short on either side of the reaction.

1. they vary with a higher number because boiling is way hotter than melting