Question

What is the [CH₃NH₃⁺] of a solution which is 0.1978 M in CH₃NH₂ and 0.1084 M in CsOH?

CH₃NH₂(aq) + H₂O(l)

Answer 1

Answer:

Kw, the equilibrium constant of water, is 1.00 e -14 = [H3O+][OH-]. Use this equation to solve - once you have [OH-], which this reaction will produce, you will be able to find [H3O+]

Start by finding [OH-] from Kb. Write the Kb expression

Kb = 1.800e-9 = [OH-][C5H5NH3] / [C5H5NH2], assuming x is very small, plugging in values gives us:
= x^2 / 0.1851 M = 1.800e-9
x = sqrt( 1.800e-9 * 0.1851 ) = 1.825e-5 = [OH-]

1.00e-14 = [H3O+] * 1.825e-5
[H3O+] = 1.00e-14 / 1.825e-5
= 5.479 e -10 M