Hydrolysis of Salts

Introduction

• Neutral solution: contains equal concentrations of hydronium and hydroxide ions.
• Acid-base neutralization reaction: the reaction between an acid and a base
• The resulting solution is not necessarily neutral, even when stoichiometrically equivalent quantities of acid and base are used.
• The nature of the salt formed determines whether the solution is acidic, basic, or neutral.

Four Types of Acid-Base Neutralizations

• Strong Acid-Strong Base: a neutral solution forms.
• Strong Acid-Weak Base: a weakly acidic solution forms.
• Weak Acid-Strong Base: a weakly basic solution forms.
• Weak Acid-Weak Base: the solution formed may be acidic or basic.

Find the pH of a Conjugate Acid in Water

• From the Kb,  find the Ka of that conjugate.
• From there on, it’s just like any other weak acid in water.

Predicting the Behavior of Salts

• Ions that contain a removable H+ can be acidic OR basic; it depends on Ka values.
• The cations of groups 1 and 2 are neutral.
  • They do not significantly react with water.
  • All OTHER cations, are acidic.
• Any – ion CAN gain a proton, and so can act as a base.
  • But it needs to be a stronger base than water, to be able to gain a proton from it.
  • The – ion from a weak acid is BASIC in water