# Homework Help: What is the pH of this new solution?

1. Jul 1, 2016

### TT0

1. The problem statement, all variables and given/known data

Equal volumes of two solutions of hydrochloric acid are mixed. One solution has a pH 1 while the other pH 5. The pH of the solution obtained is?

A) Less than 1

B) Between 1 and 2

C) 3

D) Between 4 and 5

E) More than 5

2. Relevant equations
-log[H+] = pH
10-pH = [H+]

3. The attempt at a solution
let v = volume of solution 1 added

number of mol of H+ in solution with pH 1:
10-1 * v

number of mol of H+ in solution with pH 5:
10-5 * v

molarity of H+ in new solution
$$\frac {10^{-1} * v + 10^{-5} *v} {2v}$$

therefore $$pH = -log(\frac {10^{-1} + 10^{-5}}{2})$$

Hence pH = 1.300

Is this correct?

2. Jul 2, 2016

### MexChemE

Yes, nicely done.

3. Jul 2, 2016

### TT0

Sweet, cheers!