Question

1. Determine if hydrolysis occurs for each of the following ions. If it does, write the reaction for it and determine the hydrolysis constant for each ion.

a) NO3- b) OCl- c) NH2NH3+ d) H2PO4- e) CH3NH3+

2. For each of the following ionic salts, indicate whether their aqueous solutions will be acidic, basic, or neutral.

a) Ba(NO2)2 b) Na2CO3 c) NH4ClO4 d) CH3NH3Cl e) KBr

Answer 1

1) cation hydrolysis:

M^q+(aq) + 2 H₂O(l) ? MOH^(q–1)+(aq) + H₃O⁺(aq)

If MOH^(1–q)+ is a strong base, the hydrolysis reaction does not occur. This is because the strong base completely dissociates. Thus, Group 1 and 2 metal ions (except Be²⁺) do not undergo significant hydrolysis.

For all other metal ions, the reaction is an equilibrium:

M^q+(aq) + 2 H₂O(l) MOH^(q–1)+(aq) + H₃O⁺(aq)

This reaction generates hydronium ion, so is also called acid hydrolysis.

base hydrolysis:

X^p–(aq) + H₂O(l) ? HX^(p–1)–(aq) + OH^–(aq)

If HX^(p–1)– is a strong acid, then the hydrolysis reaction cannot occur because the strong acid completely dissociates. Thus, Cl^–, Br^–, I^–, NO₃^–, ClO₄^–, and HSO₄^– do not undergo significant anion hydrolysis.

For other anions, this is an equilibrium reaction:

X^p–(aq) + H₂O(l) HX^(p–1)–(aq) + OH^–(aq)

Since hydroxide ion is generated, this reaction is also called base hydrolysis.

NO₃^- + H₂O HNO₃ + OH^-

2) the aqueous solution of salts of Na2CO3 is basic, CH3NH3Cl is neutral, KBr is basic, NH4ClO4 is acidic, Ba(NO2)2 is basic