# Calculate the pH of concentrated hydrochloric acid

1. Nov 1, 2008

### a.a

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

Calculate the pH of concentrated hydrochloric acid if this solution is 24.8 % HCl by weight and has a density of 1.16 g/mL.

2. Relevant equations

3. The attempt at a solution
\the percentage is throwing me of, can someone explain what it is?

2. Nov 1, 2008

### Gannon

Re: pH

I'm wildly guessing here, but if "percent by weight" somehow is supposed to mean "percent by mass," it would make things pretty easy; in 1.16g/mL, 28% of 1.16g would be HCl: (1.16g/mL)(0.28) = 0.3248g/mL.

From there, you can do some converting to eventually get to pH; I'll assume for now that only the percentage was tripping you up.

3. Nov 1, 2008

### a.a

Re: pH

hey, useing what u told me i think i mite be getting somewhere:

n HCl = (0.248)*(1.16g)/(36.453g/mole) = 0.0789 moles

The molar concentration is thus [HCl] = (0.00789 moles)/(0.001 lit)

= 7.89M = [H+]

pH = -log([H+]) = -0.897

can someone verify?

4. Nov 1, 2008

### Staff: Mentor

Re: pH

Yes and no. Yes - you did your best and that's probably what your teacher wants. No - in such concentrated solutions pH can't be calculated this way. But that's not your fault and you can't do anything about it.