Seema Saini Solutions for Chapter: Ionic Equilibrium, Exercise 6: DPP 7.6

An acid type indicator. $\mathrm{HIn}$ differs in colour from its conjugate base $\left({\mathrm{In}}^{-}\right).$ The human eye is sensitive to colour differences only when the ratio $\left[{\mathrm{In}}^{-}\right]/\left[\mathrm{HIn}\right]$ is greater than $10$ or smaller than $0.1$. What should be the minimum change in the $\mathrm{pH}$ of the solution to observe a colour change $\left({\mathrm{K}}_{\mathrm{In}}=1.0\times {10}^{-5}\right)$?

If at $25°\mathrm{C} \mathrm{pH}$, range of phenolphthalein is $8-10$, then at $100°\mathrm{C} \mathrm{pH}$, what would be the range of phenolphthalein?

A certain indicator (an organic dye) has ${\mathrm{pK}}_{\mathrm{a}}=5$. For which of the following titrations it may it be suitable?

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

$20 \mathrm{mL}$ of a weak monobasic acid $\left(\mathrm{HA}\right)$ requires $20 \mathrm{mL}, 0.2 \mathrm{M} \mathrm{NaOH}$ for complete titration. If the $\mathrm{pH}$ of the solution upon addition of $10 \mathrm{mL}$ of this alkali to $25 \mathrm{mL}$ of the above solution of $\mathrm{HA}$ is $5.8$, then the ${\mathrm{pK}}_{\mathrm{a}}$ of the weak acid is:

What is the difference in $\mathrm{pH}$ for $1/3$ and $2/3$ stages of neutralization of $0.1 \mathrm{M} {\mathrm{CH}}_3\mathrm{COOH}$ with $0.1 \mathrm{M} \mathrm{NaOH}$?

The pink colour of phenolphthalein in alkaline medium is due to:

Titration curves for $0.1 \mathrm{M}$ solutions of three weak acids $\mathrm{HX},\mathrm{HY}$ and $\mathrm{HZ}$ with ionization constants ${\mathrm{K}}_1,{\mathrm{K}}_2$ and ${\mathrm{K}}_3$, respectively as shown in figure below. The volume of $\mathrm{NaOH}$  added is in $\mathrm{mL}.$