Chapter 7: Problem 77
Which of the following statements is falsc? (1) Hydrolysis of the salt of strong acid and weak base is called cationic hydrolysis (2) Hydrolysis of the salt of weak acid and strong base is known as anionic hydrolysis (3) Aqueous solution of aluminium chloride is acidic due to hydrolysis of \(\mathrm{Al}^{3}\) ion (4) Aqueous solution of sodium carbonate is basic due to hydrolysis of \(\mathrm{Na}\) ion
Short Answer
Step by step solution
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
cationic hydrolysis
For example, consider ammonium chloride (NH4Cl). When it dissolves in water, it forms NH4+ and Cl- ions. The NH4+ ion undergoes cationic hydrolysis by reacting with water to form NH4OH and H+ ions.
This process makes the solution acidic because of the presence of H+ ions.
- The general reaction for cationic hydrolysis can be written as:
\text{BH\(^{+}\) + H\( _{2} \)O ↔ B + H\(_{3} \)O\(^{+}\)}
anionic hydrolysis
For instance, take sodium acetate (CH3COONa). When it dissolves in water, it forms CH3COO- and Na+ ions. The CH3COO- ion undergoes anionic hydrolysis by reacting with water to form CH3COOH and OH- ions.
This process makes the solution basic due to the presence of OH- ions.
- The general reaction for anionic hydrolysis is:
\text{A- + H\( _{2} \)O ↔ HA + OH\(^{-}\)}
acidic solutions
When salts undergo cationic hydrolysis, they often produce acidic solutions.
For example, aluminium chloride (AlCl3) in water forms Al3+ and Cl- ions. The Al3+ ion reacts with water to form Al(OH)2+ and H+ ions, increasing the H+ concentration in the solution.
This hydrolysis reaction can be written as:
\text{Al\( ^{3+} \) + 3H\(_{2}\)O ↔ Al(OH)\(_{3}\) + 3H}\(^{+}\)
- In general, solutions with high H+ concentration are acidic.
basic solutions
When salts undergo anionic hydrolysis, they often produce basic solutions.
For example, sodium carbonate (Na2CO3) in water forms Na+ and CO3^2- ions. The CO3^2- ion reacts with water to form HCO3- and OH- ions, increasing the OH- concentration in the solution.
This hydrolysis reaction can be written as:
\text{CO\(_{3}^{2-}\) + H\(_{2}\)O ↔ HCO\(_{3}^{-}\) + OH}\(^{-}\)
- In general, solutions with high OH- concentration are basic.