Weak Acid and Base Equilibria Practice Test

A $0.10,\text{M}$ solution of methylamine, $\text{CH}_3\text{NH}_2(\text{aq})$, is prepared at $25^\circ\text{C}$. For the equilibrium

$$\text{CH}_3\text{NH}_2(\text{aq})+\text{H}_2\text{O}(\ell)\rightleftharpoons \text{CH}_3\text{NH}_3^+(\text{aq})+\text{OH}^-(\text{aq}),$$

$ K_b = 4.4 \times 10^{-4} $. Which statement must be true at equilibrium?

A student prepares $0.10,\text{M}$ hydrofluoric acid, HF(aq), at $25^\circ\text{C}$. The acid dissociation constant is $K_a=6.8\times10^{-4}$. After equilibrium is established for $$ \text{HF(aq)} \rightleftharpoons \text{H}^{+}(\text{aq}) + \text{F}^{-}(\text{aq}) $$, which statement about the equilibrium concentrations is correct?