1.

Calculate the pH of a buffer containing 0.08 mole of acetic acid and 0.12 mole of sodium acetate per dm_2 of the solution. The ionisation constant of acetic acid is 1.8xx10^-5.

Answer»

SOLUTION :The pH of a buffer solution is GIVEN by the Henderson's equation .
`pH=pK_a+log.(["SALT"])/(["ACID"])`
`pK_a=-logK_a=-log[1.8xx10^(-5)]`
`=log.(1)/(1.8xx10^(-5))`
`=log 1-log1.8-log 10^(-5)`
`=5-0.2553`
`=4.7447`
`pH=4.7447+log.(0.12)/(0.08)`
`4.7447+log1.5`
`=4.7447 +0.1761`
`pH=.921.`


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