Calculate the pH during the titration of 20.00 mL of 0.1000 M trimethylamine, (CH3)3N(aq), with 0.2000 M HCl(aq) after 7.5 mL of the acid have been added. Kb of trimethylamine = 6.5 x 10-5.

The pH of the solution is 9.33

Explanation:

To calculate the number of moles for given molarity, we use the equation:

   .....(1)

Molarity of HCl solution = 0.200 M

Volume of solution = 7.5 mL

Putting values in equation 1, we get:

Molarity of trimethylamine solution = 0.100 M

Volume of solution = 20 mL

Putting values in equation 1, we get:

The chemical reaction for trimethylamine and HCl follows the equation:

Initial:             0.002      0.0015

Final:               0.0005          -         0.0015

Total volume of the solution = [20 + 7.5] = 27.5 mL = 0.0275 L   (Conversion factor:  1 L = 1000 mL)

To calculate the pH of basic buffer, we use the equation given by Henderson Hasselbalch:

where,

= negative logarithm of base dissociation constant of trimethylamine = 4.19

pOH = ?

Putting values in above equation, we get:

To calculate pH of the solution, we use the equation:

Hence, the pH of the solution is 9.33