How can you find the pH if 75 grams of HCl (hydrochloric acid) is put in 5.0L of water?

I understand that I have to convert the grams to mol, and I have the molarity, but I don't know if the concentration is of hydrogen or hydroxide ions. Can anybody help me? Thanks!

1 Answer
May 11, 2018

Well, let's see...I gets pH=0.386

Explanation:

We assume that hydrogen chloride undergoes complete protonolysis in aqueous solution...

HCl(g)+H2O(l)H3O++Cl

And so we calculate the concentration of HCl in the usual way...

[HCl]=Moles of HClVolume of solution

We ASSUME (reasonably) that the volume of THE SOLUTION is 5.0L...it would be very close...

And so...[HCl]=75g36.46gmol15.0L=0.411molL1

And so it is 0.411molL1 with respect to hydronium ions... which we represent as H3O+ or H+...

pH=log10[H3O+]=log10(0.411)=(0.386)=+0.386

The maximum concentration of HCl is approx. 10.6molL1...what is pH here...?