Question

Show why a 1 molar solution of AlCl₃ is acidic in terms of Brønsted acidity.

Answer 1

A 1 molar solution is a solution in which 1 mole of a compound is dissolved in a total volume of 1 litre.

A 1M solution that contains 1liter is prepared by weighing 133.34 grams of AlCl3 and placing this amount of salt in a 1 Liter volumetric flask and then filling the flask with distilled water to the graduation mark. 1 mole of AlCl3 = 133.34 grams

The reaction of AlCl3 with water is as follows

AlCl3 + 3 H2O === > Al(OH)3 + 3HCl

Since HCl is a strong acid , it will dissociate in water completely to form H⁺ and Cl^- ions . Hence the solution is acidic and the pH is less than 7. ( aluminium hydroxide is a weak base)

HCl is a Bronsted –Lowry acid ( donates a proton)