Question

What is the pH of a 2.0 molar solution of acetic acid? Ka=1.8x10-5

Answer 1

the ph of the solution will be 2.22.
the equaiton for Ka (ionization constant) = [H3O+][AC-]/[HAC].
as the acetic acid is weak acid its ionization will be negligible, so the [HAC] will be 2 only (as it is molar solution). and the concentration of [H3O+] and [AC-] will be same. so we can write
[H3O+]2 (square) = Ka * [HAC]
now from the concentration of [H3O+] we can find out the ph..