What is the pH of 2 M aluminium nitrate ?

1 Answer
May 17, 2017

sf(pH=2.62)

Explanation:

The ion undedrgoes hydrolysis:

sf([Al(H_2O)_6]^(3+)rightleftharpoons[Al(H_2O)_5OH]^(2+)+H^+)

You should be given sf(pK_a) for this. My Cotton and Wilkinson gives sf(pK_a=4.95).

For a weak acid a quick way to get the pH is to use the expression:

sf(pH=1/2[pK_a-loga]

Where a is the initial concentration of the solution.

:.sf(pH=1/2[4.95-(-0.3)])

sf(pH=2.62)

Small, highly charged cations like this tend to be quite acidic.