Calculate the pH of a buffer mixture which contains 7.5 gms if acetic acid and 10.25 gms of sodium acetate in 1 litre of the solution. `K_a` for acetic acid is `1.8xx10^(-5)`.

Explanation

`pH=pK_a+log.(["salt"])/(["acid"])`
The concentration of the salt and the acid should be in moles/lit.
Number of moles of acetic acid
`("weight of acetic acid")/("molecular weight of acetic acid")=(7.5)/(60)`
Number of moles of sodium acetate
`=("weight of sodium acetate")/("molecular weight of sodium acetate")=(10.25)/(82)`
`pK_a=-log K_a`
`=-log 1.8xx10^(-5)`
`=log .(1)/(1.8xx10^(-5))`
`=log 1-log 1.8-log 10^(-5)`
`=5-0.2553=4.7447`
`therefore pH=4.7447+log.(0.125)/(0.125)`
`pH=4.7447.`