Methylamine, CH₃NH₂, Is a Weak Molecular Base with a Value

Multiple Choice

Methylamine, CH₃NH₂, is a weak molecular base with a value of 4.4 × 10^-4 for K_b. An aqueous solution contains 0.200 M CH₃NH₂ and 0.400 M CH₃NH₃Cl per liter as the only solutes. If the K_sp of Mg(OH) ₂ is 7.1 × 10^-12, what is the maximum [Mg²⁺] that can coexist with these solutes in the solution?Hint: Use the Henderson-Hasselbalch formula to find the pOH of the solution, and then use that to find [OH^-].

A) 8.1 × 10^-9
B) 3.2 × 10^-8
C) 9.2 × 10^-6
D) 1.5 × 10^-4
E) 3.7 × 10^-1