Download App

Equilibrium — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryEquilibrium5 Marks
Question
The ionization constant of benzoic acid is $6.46 \times 10^{–5}$ and $K_{sp}$ for silver benzoate is $2.5 \times 10^{–13}$. How many times is silver benzoate more soluble in a buffer of pH 3.19 compared to its solubility in pure water?
✓

Answer

Since pH = 3.19,
$[\text{H}_3\text{O}^+]=6.46\times10^{-4}\text{M}$
$\text{C}_6\text{H}_5\text{COOH}+\text{H}_2\text{O}\leftrightarrow\text{C}_6\text{H}_5\text{COO}^-+\text{H}_3\text{O}$
$\text{K}_\text{a}\frac{[\text{C}_6\text{H}_5\text{COO}^-][\text{H}_3\text{O}^+]}{[\text{C}_6\text{H}_5\text{COOH}]}$
$\frac{[\text{C}_6\text{H}_5\text{COOH}]}{[\text{C}_6\text{H}_5\text{COO}^-]}=\frac{[\text{H}_3\text{O]}}{\text{K}_\text{a}}=\frac{6.46\times10^{-4}}{6.46\times10^{-5}}=10$
Let the solubility of $C_6H_5COOAg$ be xmol/L.
Then,
$[\text{Ag}^+]=\text{x}$
$[\text{C}_6\text{H}_5\text{COOH}]+[\text{C}_6\text{H}_5\text{COO}^-]=\text{x}$
$10[\text{C}_6\text{H}_5\text{COO}^-]+[\text{C}_6\text{H}_5\text{COO}^-]=\text{x}$
$[\text{C}_6\text{H}_5\text{COO}^-]=\frac{\text{x}}{11}$
$\text{K}_\text{sp}[\text{Ag}^+][\text{C}_6\text{H}_5\text{COO}^-]$
$2.5\times10^{-13}=\text{x}\Big(\frac{\text{x}}{11}\Big)$
$\text{x}1.66\times10^{-6}\text{mol/L}$
Thus, the solubility of silver benzoate in a pH 3.19 solution is $1.66 \times 10^{–6}mol/L$.
Now, let the solubility of $C_6H_5COO$ Ag be x'mol/L.
Then,
$[\text{Ag}^+]=\text{x}'\text{M and}[\text{CH}_3\text{COO}^-]=\text{x}'\text{M}.$
$\text{K}_\text{sp}=[\text{Ag}^+][\text{CH}_3\text{COO}^-]$
$\text{K}_\text{sp}=\text{(x}')^2$
$\text{x}'=\sqrt{\text{K}_\text{sp}}=\sqrt{2.5\times10^{-13}}=5\times10^{-7}\text{mol/L}$
$\therefore\ \frac{\text{x}}{\text{x}'}=\frac{1.66\times10^{-6}}{5\times10^{-7}}=3.32$
Hence, $C_6H_5COOAg$ is approximately 3.317 times more soluble in a low pH solution.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "5 Marks Questions" from Equilibrium→Equilibrium — all question types→Chemistry STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

The work function for caesium atom is $1.9eV$. Calculate,
  1. The threshold wavelength.
  2. The threshold frequency of the radiation.
If the caesium element is irradiated with a wavelength $500nm$, calculate the kinetic energy and the velocity of the ejected photoelectron.
→
In terms of period and group where would you locate the element with $Z=114$?
→
On the basis of chemical reactions involved, explain how do chlorofluorocarbons cause thinning of ozone layer in stratosphere.
→
  1. Derive the mathematical expression for first law of thermodynamics.
  2. Calculate the $\Delta_\text{r}\text{H}^\circ$ for the reaction:
$\mathrm{H}_2(\mathrm{~g})+\mathrm{Br}_2(\mathrm{~g}) \rightarrow 2 \mathrm{HBr}(\mathrm{~g})$
Bond enthalpy are given as, $\mathrm{H}-\mathrm{H}=436 \mathrm{~kJ} \mathrm{~mol}^{-1}, \mathrm{Br}-\mathrm{Br}=192 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $\mathrm{H}-\mathrm{Br}=368 \mathrm{~kJ} \mathrm{~mol}^{-1}$
→
Determine the solubilities of silver chromate, barium chromate, ferric hydroxide, lead chloride and mercurous iodide at 298 K from their solubility product constants.
1. $K _{ sp }\left( Ag _2 CrO _4\right)=1.1 \times 10^{-12}$,
2. $Ksp \left( BaCrO _4\right)=1.2 \times 10^{-10}$,
3. $K _{ sp }\left[ Fe ( OH )_3\right]=1.0 \times 10^{-3}$,
Determine also the molarities of individual ions.
→
Suggest a list of the substances where carbon can exhibit oxidation states from $-4$ to $+4$ and nitrogen from $-3$ to $+5$.
→
Explain tropospheric pollution in 100 words.
→
Calculate pH when $9.8g$ of $H_2SO_4$ is dissolved in $2L$ solution.
→
The average concentration of $\mathrm{SO}_2$ in atmosphere over a city on a certain day is 10 ppm , when the average temperature is 298 K . Given that the solubility of $\mathrm{SO}_2$ in water at 298 K is $1.3653 \mathrm{~mol} / \mathrm{L}$ and the $\mathrm{pK}_{\mathrm{a}}$ of $\mathrm{H}_2 \mathrm{SO}_3$ is 1.92 , estimate the pH of acid rain on that day.
→
Explain various methods of formation of alkynes.
→