A solution of ethanoic acid in water has a pH of 3.2. How do you calculate the concentration of the solution? K_a = 1.7 x 10^-5 mol dm^-3?

1 Answer
Dec 29, 2016

You can do it like this:

Explanation:

For a weak acid you can derive this expression from an ICE table:

sf(pH=1/2(pK_(a)-loga))

Where a is the concentration of the acid.

sf(pK_a=-logK_(a)=-log(1.7xx10^(-5))=4.77)

:.sf(3.2=1/2(4.77-loga))

sf(loga/2=2.835-3.2=-0.815)

sf(loga=-1.63)

From which sf(a=0.023color(white)(x)"mol/l")