1.

What amount of solid acetate should be added into 1 litre of the 0.1 M CH_(3)COOH solution so that the resulting solution has pH almost equal to pK_(a) (CH_(3)COOH) = 4.74.

Answer»

`12 gm`
`5 gm`
`10 gm `
`14.924 gm`

Solution :Since the resulting solution be acidic BUFFER , one may use Henderson equation.
`PH = pK_(a) + log .([CH_(3)COO^(-)])/([CH_(3)COOH]) `
LET n mol of `CH_(3)COONa` be added to do so
or , `pH = 4.74 + log[((n(mol))/(v(L)))/((0.1(mol))/(v(L)))] " or , " 5 = 4.74 + log [n/(0.1)]`
or, `log . n/(0.1) = 0.26 "or," n/(0.1) = " antilog " 0.26 = 1.8197`
`:. n = 0.1897 mol ~= 0.182 ` mol
amount of sodium acetate = `0.182 xx 82 gm = 14.924` gm


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