Question

Find the ph of a buffer that consists of 0.18 m ch3nh2 and 0.73 m ch3nh3cl (pkb of ch3nh2 = 3.35)?

Answer 1

Hello!

First, we need to determine the pKa of the base. It can be found applying the following equation:

$pKa=14-pKb=14-3,35=10,65$

Now, we can apply the Henderson-Hasselbach's equation in the following way:

$pH=pKa+log( \frac{[CH_3NH_2]}{[CH_3NH_3Cl]} )=10,65+log( \frac{0,18M}{0,73M} )=10,04$

So, the pH of this buffer solution is 10,04

Have a nice day!