Question

What is the pH of a buffer solution that contains 0.55 M methylamine, CH 3NH2, and 0.29 M methylammonium chloride, CH3NH3Cl?A

Answer 1

pH = 10.93

Step-by-step explanation:

To find the pH we need to use the Henderson - Hasselbalch equation:

`pH = pKa + log(([A^(-)])/([HA]))`

Where:

[A⁻]: is the conjugate base of the acid = [CH₃NH₂] = 0.55 M

[HA]: is the acid = [CH₃NH₃Cl] = 0.29 M

Since the pkb of methylamine is 3.35, the pka is:

`pk_(a) + pk_(b) = 14`

`pk_(a) = 14 - pk_(b) = 14 - 3.35 = 10.65`

Now, the pH is:

`pH = pKa + log(([A^(-)])/([HA])) = 10.65 + log((0.55)/(0.29)) = 10.93`

Therefore, the pH of the buffer solution is 10.93.

I hope it helps you!