Question

What volume of 1.35 M HCl must be added to 0.236 L of 0.323 M dimethylamine to produce a buffer with a pH of 10.73? Dimethylamine has the formula (CH3)2NH, a Kb value of 5.89.

a) Depends on temperature
b) Not enough information
c) Calculated value
d) 42.0 L

Answer 1

The volume of 1.35 M HCl needed to create a buffer solution with dimethylamine can be calculated using the Henderson-Hasselbalch equation, which relates pH to the pKa and the ratio of the concentrations of the acid-base pair in the buffer.

Step-by-step explanation:

The question asks about the calculation of the volume of 1.35 M HCl required to create a buffer solution when added to a known volume and concentration of dimethylamine. This is a typical acid-base buffer problem in chemistry that involves the Henderson-Hasselbalch equation, which is used to relate the pH of a buffer solution to the pKa and the ratio of the concentrations of the conjugate acid-base pair.

To calculate the volume of HCl needed, we need to know the moles of dimethylamine and its conjugate acid, dimethylammonium ion [(CH3)2NH+], present in the solution at the desired pH. Using the pH and the Kb (or pKb) of dimethylamine, we can find the ratio of the acid and base using the Henderson-Hasselbalch equation. Then we can calculate how many moles of HCl are needed to achieve this ratio and thus determine the volume of the HCl solution that must be added.