A change in pH of 1.0 unit indicates that:_____.
1. the molarity of H changes by one order of magnitude.
2. the volume of H in a solution changes by an order of magnitude.
3. the acid or base content decreases or increases by 1.0 M.
4. the acid or base content decreases or increases by 0.1 M.
5. the salt content decreases or increases by 1.0 M.