Calculating PH Levels HELP!!!!

[txen]

Originally Posted by tm20

I have to write a report about the experiment I did with my group on enzyme activity in different pH and temperatures. I need to calculate the pH levels of the following solutions:

5mL of H2O2 + 1mL of 0.1M HCl
5mL of H2O2 + 1mL of 1M HCl
5mL of H2O2 + 1mL of 0.1M NaOH
5mL of H2O2 + 1mL of 1M NaOH

and I don't know what to do I've read some information on the internet and it says the pH is the negative log of the molarity. so it has an example:

pH of a 0.0025 M HCl solution = -log(0.0025) = 2.6

but since I have a combination of 2 chemicals, is it -log(M1+M1) or -log(M1) + -log(M2)? If you can help me it would be greatly appreciated

Kids these days, don't they teach you anything? Just kidding. You are on the right track.

First question. You mean H20 (water) or H2O2(hydrogen peroxide)? Pure H2O2 is dangerous and adding HCl just makes it worse. Hope it's just a book problem. Heck H2O2 in water is a weak acid in itself. It's go to be water.

If it is actually water then you are correct about how to calculate it. 5ml H2O and 1ml of .1M HCl would give .0167M HCl. Then do the negative log thing.

For bases (NaOH) you use the fact that [H+][OH-] = 10 to the minus 7

That's how I remember it and I haven't touched a chemistry book for 25 years.