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=0.386pH=0.386

Explanation:

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

HCl(g) +H_2O(l) rarrH_3O^+ + Cl^-HCl(g)+H2O(l)H3O++Cl

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

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

We ASSUME (reasonably) that the volume of THE SOLUTION is 5.0*L5.0L...it would be very close...

And so...[HCl]=((75*g)/(36.46*g*mol^-1))/(5.0*L)=0.411*mol*L^-1[HCl]=75g36.46gmol15.0L=0.411molL1

And so it is 0.411*mol*L^-10.411molL1 with respect to hydronium ions... which we represent as H_3O^+H3O+ or H^+H+...

pH=-log_10[H_3O^+]=-log_10(0.411)=-(-0.386)=+0.386pH=log10[H3O+]=log10(0.411)=(0.386)=+0.386

The maximum concentration of HClHCl is approx. 10.6*mol*L^-110.6molL1...what is pHpH here...?