The phenomenon of interaction of anions and cations furnished by an electrolyte with the H+ and OH- ions of water to produce acidic nature or alkalinity is known as hydrolysis. In hydrolysis:
1. the pH may either increase or decrease
2. all the salts (except those made up with strong acid and base) undergo hydrolysis
3. the variation of pH depends upon the nature of salts as well as on the temperature
4. all of the above