Calculate the ratio of CH3NH2 to CH3NH3Cl required to create

Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH= 10.18.

Solution

Use the equation pH = pKa + log([Base]/[Acid])
Since we are calculating for [Base]/[acid], lets set it equal to x
pH = pKa + log(x)

The Kb of CH3NH2 is 4.4*10^-4.
pKb = 3.35
pKa+pKb = 14
pKa = 10.64 (check this number to make sure it\'s accurate)

pH = 10.64 + log(x)
plug in the pH value
10.18 = 10.64 + log(x)
=0.346