I have 25 million gallons of water at a pH of 6.5. I add 17.4 million gallons of 12.5% by wt sodium hypochlorite (NaClO) at a pH of 12.5 to this water. What will my pH of my final solution be?

It's been about 5 years since I took chemistry and I just don't remember how to even start this. I know pH is -log[H+]
Thanks in advance

3 answers

Figure the concentration of H+ in each one, convert that concentration(s) to moles in each one, add them, divide by the new volume. Then, figure the pH of that amount.

conc H+ = 10^-pH
So I convert from H+ concentration to moles by just using the molecular weight of a proton?
Also, that will eventually give me molarity mol/L but then how do I go from there to pH?
Not quite. mols in each = M x L = ?
Then after you know (H^+) in mols/L (i.e., molarity) then use the pH formula Bob Pursley gave you in the last line to get pH.