Question

A 0.15M solution of methylamine CH3NH2 contains an unknown concentration of methylamine chloride CH3NH3Cl. If the solution has a pH of 10.20,what is the concentration of methylamine chloride in the solution? Kb for methylamine=4.6*10^-4

Answer 1

0.43 M

Step-by-step explanation:

The equation that should be used in this case would be:
pOH = pKb + log([A+]/[Base])
pKb = -log (4.6*10^-4) = 3.34
pOH = 14-10.2 = 3.8
[Base] = 0.15
3.8 = 3.34 + log x/0.15
0.46=log x/0.15
10^(0.46) = x/.15
x = 10^(0.46) * 0.15 = 0.43 M