Question

71% Calculate the pH and concentration of all species in a 027M Na2 SOs (sodium sulfite) solution? The ionization constants for sulfurous acidare Kal 1.4 x 10-2 and K2 6.3 x 10-8 Give your answers to 2 significant figures OH 1 POH PH- İHS S05 -

Answer 1

concentration of Na2SO3 = 0.27 M

Ka1 = 1.4 x 10^-2 , Ka2 = 6.3 x 10^-8

concentration of Na+ = 2 x 0.27 = 0.54 M

SO32- +   H2O    -----------> HSO3- + OH-

0.27                                          0              0

0.27 - x                                     x              x

Kb1 = x^2 / 0.27 - x

Kw / Ka2 = x^2 / 0.27 - x

1.59 x 10^-7 = x^2 / 0.27 - x

x = 2.07 x 10^-4

[OH-] = 2.07 x 10^-4 M

pOH = -log [OH-] = -log (2.07 x 10^-4 )

         = 3.68

pH = 10.32

Kb = 1.6 x 10^-7

[OH-] = 2.1 x 10^-4 M

[H+] = 4.8 x 10^-11 M

pOH = 3.7

pH = 10.

[Na+] = 0.54 M

[SO32-] = 0.27 M

[HSO3-] = 2.1 x 10^-4 M

[H2SO3] = 7.1 x 10^-13 M