Chemical reactions need to be balanced. There must be an equal number of each type of atom on each side of the reaction arrow. For example,
NH3 + H2O -> OH- + NH4+
Is balanced and correct. On the reactant side, there are 1 N, 5H, and 1O, and on the product side there are 1N, 5H, and 1O.
HCLO4 + H20 -> H+ + CLO4-
This, on the other hand, is not balanced. Here you have 3H, 1Cl, and 5O on the reactant side, but 1H, 1Cl, and 4O on the product side. There is an imbalance of two hydrogens and one oxygen. That should give you a clue of how to fix the reaction.
Checking whether your chemical equations are balanced is a good first check on whether your equation will work or not.