Question

When equal volumes of ph=4 and ph=6 are mixed together then the ph?

Answer 1

V1 = V2 = V (say)
pH = 4
or [H+] = 10^(-4)
So molarity of first solution, M1 = 10^(4) M
Similarly for the second solution, M2 = 10^(-6) M

Now M1V1 + M2V2 = M(V1+V2) , where M is the Molarity of [H+] for the final solution.

or 10^(-4) V + 10^(-6)V = 2MV
or 1.01 × 10^(-4) V = 2MV
or M = 5.05 × 10^(-5)

So pH of resulting solution = -log(5.05×10^(-5)) = 4.3