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

Buffer capacity of a buffer solution is $\mathrm{x}$, the volume of $1 \mathrm{M} \mathrm{NaOH}$ added to $100 \mathrm{mL}$ of this solution if change the $\mathrm{pH}$ by $1$ is:

What fraction of an indicator $\mathrm{Hln}$ is in basic form at a $\mathrm{pH}$ of $6$ if the ${\mathrm{pK}}_{\mathrm{a}}$ of the indicator is $5?$

An acid-base indicator which is a weak acid has a ${\mathrm{pK}}_{\mathrm{In}}$ value $=5.45$. At what concentration ratio of sodium acetate to acetic acid would the indicator show a colour halfway between those of its acid and conjugate base forms? [${\mathrm{pK}}_{\mathrm{a}}$ of acetic acid $=4.75, \log 2=0.3$]

The solubility curve of ${\mathrm{KNO}}_3$ as a function of temperature is given below:

The amount of ${\mathrm{KNO}}_3$ that will crystallize when a saturated solution of ${\mathrm{KNO}}_3$ in $100 \mathrm{ml}$ of water is cooled from $90°\mathrm{C}$ to $30°\mathrm{C}$, is:

The reaction,

$2 \mathrm{A}\left(\mathrm{g}\right)+\mathrm{B}\left(\mathrm{g}\right)\rightleftharpoons 3\mathrm{C}\left(\mathrm{g}\right)+\mathrm{D}\left(\mathrm{g}\right)$

is begun with the concentrations of $\mathrm{A}$ and $\mathrm{B}$ both at an initial value of $1.00 \mathrm{M}.$ When equilibrium is reached, the concentration of $\mathrm{D}$ is measured and found to be $0.25 \mathrm{M}.$ The value for the equilibrium constant for this reaction is given by the expression:

At what $\mathrm{pH}$ will a $1\times {10}^{-4} \mathrm{M}$ solution of an indicator $\left({\mathrm{K}}_{\mathrm{b}}\right.$ indicator$=1\times {10}^{-11}$$)$ change colour?

Calculate the $\mathrm{pH}$ of a $0.01 \mathrm{M} {\mathrm{NaHCO}}_3$ solution $[\left[{\mathrm{K}}_1\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)=4\times {10}^{-7}, {\mathrm{K}}_2\left({\mathrm{HCO}}_3^{-}\right)=4.8\times {10}^{-11}\right]$ for carbonic acid$]$. The reactions are:
$$\begin{gathered} {\mathrm{H}}_2{\mathrm{CO}}_3\rightleftharpoons {\mathrm{H}}^{+}+{\mathrm{HCO}}_3^{-}; {\mathrm{K}}_1 \\ {\mathrm{HCO}}_3^{-}\rightleftharpoons {\mathrm{H}}^{+}+{\mathrm{CO}}_3^{2-}; {\mathrm{K}}_2 \end{gathered}$$

Blood plasma is maintained at a $\mathrm{pH}$ of $7.4$ largely by the