Question

The pH of a solution is 7. When acid is added to the solution, the hydronium ion concentration becomes 100 times greater. What is the pH of the new solution?

A) 14
B) 9
C) 1
D) 5

Answer 1

It's D <<<<====
For every power of 10, the pH goes down 1. 7 is neutral. As you add acid, the pH will decrease.

If you start out with a pH of 7 and you add a base the pH will go up. That's practically the only rule you need.