1.

(b) What volume of 0.6 M sodium formate solution is required to prepare a buffer solution is required to prepare a buffer solution of pH 4.0 by mixing it with 100 ml of 0.8 M formic acid . (Given pK_(a)for formic acid is 3.75).

Answer»

SOLUTION :(b) `pH=pK_(a)+LOG (["salt"])/(["acid")]`
`4=3.75+log. (["Sodium FORMATE"])/(["formic acid"])`
[ Sodium formate] = NUMBER of MOLES of `HCOONa`
`=0.6xxVxx10^(-3)`
`=80xx10^(-3)`
`4=3.75+log.(0.6V)/(80)`
`0.25 = log.(0.6V)/(80)`
antilog of `0.25=0.6 V`
`0.6V-1.778xx80`
`=1.78xx80`
`=142.4`
`V=(142.4 mL )/(0.6)=237.33 mL `


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