Suppose it is required to make a buffer solution of `pH=4`. Using acetic acid and sodium acetate. How much of sodium acetate to be added to `1` litre of `N//10` acetic acid ? Dissociation constant of acetic acid is `1.8xx10^(-5)`.

Explanation

Applying Henderson.s equation,
`pH=pK_(a)+log.(["salt"])/(["acid"])`
`pH=log.(["salt"])/(["acid"])-logK(a)`
`4={log["salt"]-log(0.1)}-log(1.8xx10^(-5))`
`log("salt")=4-1-5+0.2552=bar2.2522`
`["salt"]=0.018mol L^(-1)`
The molecular mass of `CH_(3)COONa=82`
Amount of salt `=0.018xx82=1.476g`.