Acids and bses

1 mL of a strong acid solution has a pH of 2.3. It is diluted with water to make a 100 mL solution. What is the new pH?

I don't really understand the concepts behind this question, could someone show how to work it out using definitions?

Also, with this question, and from my past few days of studying, I'm starting to get very worried. I am forgetting some of the most basic concepts from my prereq classes, and I have been studying for this exam for 3 months now. Nothing is really sticking;...

Acids and bses