Question

Calculate the ratio of ch3nh2 to ch3nh3cl required to create a buffer with ph = 10.28. express your answer using two significant figures.

Answer 1

Hello!

The chemical reaction for the ionization of CH₃NH₂ is the following:

CH₃NH₂ + H₂O ⇄ CH₃NH₃⁺ + OH⁻ pKb=3,30


`pKa=14-pKb=14-3,30=10,70`

Now we apply the Henderson-Hasselbach equation and clear for the ratio of CH₃NH₂ to CH₃NH₃Cl:


`pH=pKa+log( ([CH_3NH_2])/([CH_3NH_3Cl]) ) \\ \\([CH_3NH_2])/([CH_3NH_3Cl])= 10^((pH-pKa))= 10^((10,28-10,70))=0,38`

So, the ratio of CH₃NH₂ to CH₃NH₃Cl is 0,38

Have a nice day!