Embibe Experts Solutions for Chapter: Equilibrium, Exercise 3: Level 3

Which of the following curves represents a very rare standard reactivity at equilibrium?

The solubility product $\left({\mathrm{K}}_{\mathrm{sp}}\right)$ of salts of types $\mathrm{MX}, {\mathrm{MX}}_2$ and ${\mathrm{M}}_3\mathrm{X}$ at a temperature ${}^{\text{'}}\mathrm{T}^{\text{'}}$ are $4.0\times {10}^{-8},3.2\times {10}^{-14}$ and $2.7\times {10}^{-15}$ respectively. Solubilities $\left(\mathrm{mol} {\mathrm{dm}}^{-3}\right)$ of salts at temperature $\text{'}$$\mathrm{T}$$\text{'}$ are in the order:

$2.5 \mathrm{mL}$ of $\frac{2}{5} \mathrm{M}$ weak monoacidic base $\left({\mathrm{K}}_{\mathrm{b}}=1\times {10}^{-12} \text{at} 25°\mathrm{C}\right)$ is titrated with $\frac{2}{15} \mathrm{M} \mathrm{HCl}$ in water at $25°\mathrm{C}$. The concentration of ${\mathrm{H}}^{+}$ at the equivalence point is $\left({\mathrm{K}}_{\mathrm{w}}=1\times {10}^{-14} \text{at} 25°\mathrm{C}\right)$.

(Hint: The base is very weak, the cations of the salt formed at the equivalence point shall undergo hydrolysis to a greater extent and, hence, the degree of hydrolysis $\left(\mathrm{h}\right)$ cannot be neglected in comparison to $1$. Now, apply ${\mathrm{K}}_{\mathrm{h}}=\frac{{\mathrm{Ch}}^2}{1-\mathrm{h}}=\frac{{\mathrm{K}}_{\mathrm{w}}}{{\mathrm{K}}_{\mathrm{b}}}; \mathrm{C}=0.1 \mathrm{M}, \left[{\mathrm{H}}^{+}\right]=\mathrm{Ch}$).

Calculate the molar solubility of  $\mathrm{AgCl}$ in $1.0 \mathrm{M} {\mathrm{NH}}_3.{\mathrm{K}}_{\mathrm{sp}}\left(\mathrm{AgCl}\right)=1.8\times {10}^{-10}, {\mathrm{K}}_{\mathrm{f}} \left(Ag{\left({\mathrm{NH}}_3\right)}_2^{+}\right)=1.7\times {10}^7$.

Give your answer up to two places of decimal.

Calculate the $\mathrm{pH}$ at the equivalence point, when a solution of $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}$ is titrated with a solution of $0.1 \mathrm{M} \mathrm{NaOH}$, ${\mathrm{K}}_{\mathrm{a}}\left({\mathrm{CH}}_3\mathrm{COOH}\right)=1.8\times {10}^{-5}$.

$(\mathrm{Choose} \mathrm{your} \mathrm{answer} \mathrm{from} \mathrm{these} \mathrm{values} : 4.74/8.72/11.74/7.12)$

The value of ${\mathrm{K}}_{\mathrm{p}}$ for the reaction ${\mathrm{PCl}}_5\rightleftharpoons {\mathrm{PCl}}_3+{\mathrm{Cl}}_2$ is $1.78$ at $250°\mathrm{C}$. The fraction of dissociation is $\mathrm{a} \times {10}^{-4}$ at equilibrium when $0.40$ mole of ${\mathrm{PCl}}_5$ is vaporised in a vessel containing $0.20$ mole of ${\mathrm{Cl}}_2$ gas when the volume is kept constant at $4$ litres.

Calculate the value of $\mathrm{a}$.

$K_a$ for butyric acid is $2.0\times {10}^{-5}$. Calculate the $\mathrm{pH}$ of $0.2 \mathrm{M}$ aqueous solution of sodium butyrate.

Consider the equilibrium: $\mathrm{LiCl}.3{\mathrm{NH}}_3 \left(\mathrm{s}\right)\rightleftharpoons \mathrm{LiCl}.{\mathrm{NH}}_3 \left(\mathrm{s}\right)+2{\mathrm{NH}}_3 \left(\mathrm{g}\right)$ with ${\mathrm{K}}_{\mathrm{p}}=9 {\mathrm{atm}}^2$ at $40 °\mathrm{C}.$ A$5 \mathrm{litre}$ flask contains $0.1 \mathrm{mole}$ of $\mathrm{LiCl}·{\mathrm{NH}}_3$. How many moles of ${\mathrm{NH}}_3$ should be added to the flask at this temperature to drive the backward reaction practically to completion?