Which solution has the lower PH 0.1 M HCL or 0.1 M HC2H302. Explain why?

1 Answer
anor277
Apr 19, 2018

The #pH# of the hydrochloric acid solution will be LOWER....

Explanation:

By definition, #pH=-log_10[H_3O^+]#. Hydochloric acid is a STRONG acid...for which we may assume that protonolysis in quantitative...

#HCl(aq) +H_2O(l)rarr H_3O^+ + Cl^(-)#

And so #[H_3O^+]=0.1*mol*L^-1#...and thus #pH=-log_10(10^-1)=-(-1)=+1#...

For acetic acid, protonolysis will not be so complete, and #[H_3O^+]"<<"0.1*mol*L^-1#...and thus #pH">>"+1#. You could solve for #pH# exactly had you included #K_a("acetic acid")#...

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