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A typical sample of vinegar has a pH of 3.0. Assuming that vinegar is only an aqueous solution of acetic acid (Ka=1.8x10^-5), calculate the concentration of acetic acid in vinegar.

Answer :

Answer: Concentration of acetic acid in vinegar is 0.06 M

Explanation:

[tex]CH_3COOH\rightleftharpoons CH_3COO^-+H^+[/tex]

     cM              0             0

[tex]c-c\alpha[/tex] [tex]c\alpha[/tex] [tex]c\alpha[/tex]

So dissociation constant will be:

[tex]K_a=\frac{(c\alpha)^{2}}{c-c\alpha}[/tex]

[tex]pH=-log[H^+][/tex]

[tex]3.0=-log[H^+][/tex]

[tex][H^+]=c\times \alpha=10^{-3}[/tex]

[tex]K_a=1.8\times 10^{-5}[/tex]

Putting in the values we get:

[tex]1.8\times 10^{-5}=\frac{(10^{-3})^2}{(c-10^{-3})}[/tex]

[tex]c=0.06M[/tex]

Thus concentration of acetic acid in vinegar is 0.06 M

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