# How do you calculate the pH at the equivalence point for the titration of .190M methylamine with .190M HCl? The Kb of methylamine is 5.0x10^-4.

##### 1 Answer

#### Explanation:

The net ionic equation for the titration in question is the following:

This exercise will be solved suing two kinds of problems: **Stoichiometry problem** and **equilibrium problem** .

**Stoichiometry Problem** :

At the equivalence point, the number of mole of the acid added is equal to the number o fmole of base present.

Since the concentrations of base and acid are equal, the concentration of the conjugate acid

Since equal volumes of the acid and base should be mixed, and since they are additive, the concentration of

Thus,

**Equilibrium Problem** :

The conjugate acid that will be the major species at the equivalence point, will be the only significant source of

Note that

Solve for

Therefore, the pH of the solution is

Here is a video that explains in details the titration of a weak acid by a strong base:

**Acid - Base Equilibria | Weak Acid - Strong Base Titration.**