The charge balance equation of species in 0.100 M acetic solution is given by

Options

A. `[H^(+)] = [OH^(-)] `
B. `[H^(+)] =[CH_(3)COO^(-)]`
C. `[H^(+)] = [OH^(-)] +[CH_(3)COO^(-)]`
D. `2[H^(+)]=[OH^(-)] +[CH_(3)COO^(-)]`

Answer

C

Explanation

The equilibrium are
`CH_(3)COOH hArrH^(+) +CH_(3)COO^(-)`
`H_(2)O hArrH^(+) +OH^(-)`
As analytical concentration of acetic acid is equal to the sum of the equilibrium concentrations of all its species. `C_(CH_(3)COOH)= [CH_(3)COOH] +[CH_(3)COO^(-)]=0.100M `
A second mass balance expression may be written for the equilibrium concentration of `H^(+)`which is derived from both `CH_(3)COOH and H_(2)O ` . We obtain one `H^(+)` for each `CH_(3)COO^(-)` and one for each `OH^(-)`
`[H^(+)] = [CH_(3)COO^(-)] +[OH^(-)] `
Note : In a mass balance, the analytical concentration is equal to the sum of the concentrations of the equilibrium species derived from the parent compound.