Question

The pKs of succinic acid (HOOC-CH2-CH2-COOH) are 4.21 and 5.64. How many grams of monosodium succinate (NaOOC-CH2-CH2-COOH) and disodium succinate (NaOOC-CH2-CH2-COONa) must be added in order to prepare 1 L of a 0.1M buffer at pH 5.28? Give your answer in grams of monosodium succinate and grams of disodium succinate, respectively.

Answer 1

pH = pka2 + log [Na2C4H4O2] /[NaC4H5O2]

5.28 = 5.64 + log [disodium succinate]/[monosodium succinate]

0.4365 [monosoium succinat] = [disodium succinate] ................(1)

Buffer conc = 0.1 M = [monosodium succinate] + [disodium succinate] ...........(2)

based ( 1) ( 2) , we get [ monosodium succinate] = 0.0696136

[disodium succinate] = 0.03038636

Moles = M x V , where V = 1L , hence Moles of monosodium succinate = 0.0696136

moles of diodium succinate = 0.03038636

Mass of monosidum succinate = Moles x molar mas s= 0.0696136 x 140.07= 9.75 g

Mass of disodium succinate = Moles x molar mass = 0.03038636 x 162.05 = 4.924 g