Question

if equal volumes of solutions having pH6 and pH7 are mixed what is the resulting pH?

Answer 1

It isn't pH 6.5.
You must determine (H^+) from pH 6 and (H^+) from pH 7, average them, then determine pH from that new (H^+).

Answer 2

great thanks a lot, soz bout double post

Answer 3

Here are the initial steps of the solution DrBob suggested:

Let V = liters of solution.
moles of H+ with pH 6 is = 1.00x10^-6)(V)
The total moles of H+ in the mixture is:
moles H+ = (1.00x10^-6)(V)+(1.00x10^-7)(V)
[H+] = (moles H+)/V