Question

Predict acid–base properties of salts.

What is the acid-base nature of the following salts?

Ka(HCN) = 4.00×10-10; Kb((CH3)3N) = 6.3×10-5; Ka(HNO2) = 4.5×10-4

(a) barium cyanide, Ba(CN)2 : acidic, basic, or neutral

(b) trimethylammonium nitrite, [(CH3)3NH]NO2 : acedic, basic, or neutral

Answer 1

Salts are formed as a result of reaction between acids and bases. When the salt dissolves in water, if it gives H⁺ ions, then it is acidic and when it gives OH^-, it is basic.

(a) Barium cyanide ( Ba(CN)₂ ):

When barium cyanide is dissolved it water, it results in the formation of barium hydroxide (Ba(OH)₂) and hydrogen cyanide (HCN). Since Ba(OH)₂ is a strong base and HCN is a weak acid, the corresponding salt barium cyanide will be basic in nature.

(b) Trimethylammonium nitrite ([(CH₃)₃NH]NO₂):

When trimethylammonium nitrate dissolved in water, it results in the formation of trimethylamine and nitrous acid. Since nitrous acid is a strong acid, the salt is acidic in nature.