1.

Find the pH of a buffer solution containing 0.20 mole per litre sodium acetate and 0.18 mole per litre acetic acid, K_a for acetic acid is 1.8 times 10^-5.

Answer»

Solution :`ph=Pk_a+LOG([salt])/([acid])`
GIVEN that `K_a=1.8 TIMES 10^-5`
`THEREFORE pK_a=-log(1.8 times 10^-5)`
`=5-log 1.8`
`=5-0.26=4.74`
`therefore pH=4.74+log (0.20)/(0.18)`
`=4.74+log 10/9`
`=4.74 +log 10/9`
`4.74+1-0.95`
`=5.74-0.95`
`=4.79`


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