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) +H_2O(l) rarrH_3O^+ + Cl^-

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

[HCl]="Moles of HCl"/"Volume of solution"

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

And so...[HCl]=((75*g)/(36.46*g*mol^-1))/(5.0*L)=0.411*mol*L^-1

And so it is 0.411*mol*L^-1 with respect to hydronium ions... which we represent as H_3O^+ or H^+...

pH=-log_10[H_3O^+]=-log_10(0.411)=-(-0.386)=+0.386

The maximum concentration of HCl is approx. 10.6*mol*L^-1...what is pH here...?