College

Consider a buffer made by adding 35.9 g of [tex](CH_3)_2NH[/tex] to 250.0 mL of 1.42 M [tex](CH_3)NH[/tex] (Kb = [tex]5.4 \times 10^{-4}[/tex]).

What is the pH of the buffer after 0.300 mol of [tex]H^+[/tex] have been added?

Answer :

Final answer:

A buffer solution is used to resist changes in pH. The pH of the buffer after adding 0.300 mol of H+ can be calculated using the Henderson-Hasselbalch equation.


Explanation:

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added. In this case, the (CH3)2NH₂ and (CH3)NH are part of a buffer solution. The (CH3)2NH₂ acts as a weak base and (CH3)NH acts as its conjugate acid.

To calculate the pH of the buffer after adding 0.300 mol of H+, we need to consider the chemical reaction:

(CH3)2NH₂ + H+ ⇌ (CH3)NH₂ + H2O

Since we're adding 0.300 mol of H+, we expect the reaction to shift to the right, consuming some of the (CH3)2NH₂ and producing (CH3)NH₂. The remaining (CH3)2NH₂ and (CH3)NH will then generate a specific pH based on their concentrations.

To find the pH, concentration of (CH3)2NH₂, and concentration of (CH3)NH, we need to use the given mass (35.9 g) and volume (250.0 mL) of (CH3)2NH₂, as well as the molarity of (CH3)NH (1.42 M). From there, we can calculate the pH using the Henderson-Hasselbalch equation.


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