Question

Compound A${}_{\left(l\right)}$ and B${}_{\left(l\right)}$ function as a weak acid and weak base respectively when dissolved in water. When pure A${}_{\left(l\right)}$ is dissolved in anhydrous B${}_{\left(l\right)}$, A will function as:

• A. an acid
• B. a base
• C. a stronger acid than when dissolved in $H_{2}O$
• D. a stronger base than when it is dissolved in $H_{2}O$

Answer 1

Answer: (A), (C)

The correct options are
A an acid
C a stronger acid than when dissolved in $H_{2}O$

$A_{\left(l\right)}+H_{2}O\stackrel{K_a}{\rightleftharpoons }{A}^{\prime }\left(aq\right)+H_2{O}^{+}$

$B_{\left(l\right)}+H_{2}O\stackrel{K_b}{\rightleftharpoons }B{H}^{+}aq+O{H}^{-}$

$A_{\left(l\right)}+B_{\left(l\right)}+2H_{2}O\stackrel{K_a{K}_b}{\rightleftharpoons }{A}^{\prime }+B{H}^{+}+H_3{O}^{+}{H}_3{O}^{+}+O{H}^{-}\stackrel{K_w}{\rightleftharpoons }2H_{2}O$

$A_{\left(l\right)}+B_{\left(l\right)}\underset{K_w}{\stackrel{K_a{K}_b}{\rightleftharpoons }}{A}^{\prime }+B{H}^{+}$

Now, suppose $\frac{K_a{K}_b}{K_w}>K_a$

$\Rightarrow$ $K_b>K_w$, which is true because B is a stronger base than $H_{2}O$ and hence, our assumption is correct.

$\Rightarrow A\left(l\right)$ is a stronger acid in $B\left(l\right)$ compared to an aqueous medium.

Hence, the correct options are $\text{A}$ and $\text{C}$