What will be the hydrogen ion concentration of a solution obtained by mixing 500ml of 0.2 M acetic acid and 500ml of 0.4 M sodium acetate ? `(K_(a)CH_(3)COOH)=1.8 xx 10^(-5))`

Options

A. `1.8 xx 10^(-5)`
B. `0.9 xx 10^(-6)`
C. `9 xx 10^(-6)`
D. `1.6 xx 10^(-4)`

Answer

C

Explanation

`CH_(3)COOH hArr CH_(3)COO^(-)+H^(+)`
`K_(a)=([CH_(3)COO^(-)][H^(+)])/([CH_(3)COOH])`
`:. [H^(+)]=K_(a).(["acid"])/(["Salt"])`
`=1.8 xx 10^(-5)xx(0.1)/(0.2)=9 xx 10^(-6)`