# Acids, concentrations, percentages, pH, and molarity

## Recommended Posts

I'm sure this has been asked NA times, but I haven't been able to find a clear answer -- just bits and pieces as parts of larger discussions. My chemistry classes are many years in the past now, so I might not even be asking sensible questions. However..

I'm looking for formulae relating concentrations, pH, and molarity to each other, for strong acids/bases. For example, I have here a bottle of industrial H2SO4 for which the MSDS claims the 'Hazardous Components: Sulfuric Acid 93.2%'. Is it safe to assume that's w/w? Presuming the other 6.8% is water, how can I determine the molarity and pH?

##### Share on other sites

• 2 weeks later...

I finally managed to phrase my search in such a way as to find something useful: http://www.chembuddy.com/?left=concentration-questions&right=mass-percentage-to-molarity-q1. Given that, and the best MSDS I could find for this bottle of Rooto drain opener, and assuming the solvent is H2O, and that the figures on the ChemBuddy site are accurate, and linearly interpolating the density of 93.2% H2SO4, I get this:

m[sub]H[sub]2[/sub]SO[sub]4[/sub][/sub] = 98.07848
d[sub]H[sub]2[/sub]SO[sub]4[/sub][/sub] = 1.821761 (interpolated)
c[sub]M[sub]H[sub]2[/sub]SO[sub]4[/sub][/sub][/sub] = (10 × 93.2 × 1.821761) ÷ 98.07848
= 17.3114537


The only figure there that's accurate is the molar mass of H2SO4; the density is interpolated from a w/w concentration that may or may not be accurate.

However, the result of approximately 17 molar seems about right to me.

Did I do this correctly, or did I screw up somewhere?

Now on to figuring out the pH..

##### Share on other sites

• 4 weeks later...

I have a slightly higher value for the density, but otherwise you are right on track.

##### Share on other sites

Sounds right. Now If you want a hint I suggest you look up formulas for finding the pH of diprotic acids.

## Create an account or sign in to comment

You need to be a member in order to leave a comment

## Create an account

Sign up for a new account in our community. It's easy!

Register a new account