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#?

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Answer 1 · 2016-12-29T10:40:57

You can do it like this:

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")#