Andhra Pradesh Board Solutions for Chapter: Solutions, Exercise 5: Questions

A solution containing $30 \mathrm{g}$ of non-volatile solute exactly in $90 \mathrm{g}$ of water has a vapour pressure of $2.8 \mathrm{kPa}$ at $298 \mathrm{K}$. Further, $18 \mathrm{g}$ of water is then added to the solution and the new vapour pressure becomes $2.9 \mathrm{kPa}$ at $298 \mathrm{K}$. Calculate the vapour pressure at $298 \mathrm{K}$.

Two elements A and B form compounds having formula ${\mathrm{AB}}_2$and ${\mathrm{AB}}_4$ . When dissolved in $20 \mathrm{g}$ of benzene $\left({\mathrm{C}}_6{\mathrm{H}}_6\right)$, $1 \mathrm{g}$ of ${\mathrm{AB}}_2$ lowers the freezing point by $2.3 \mathrm{K}$ whereas $1.0 \mathrm{g}$of ${\mathrm{AB}}_4$ lowers it by $1.3 \mathrm{K}$. The molar depression constant for benzene is $5.1 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}$. Calculate atomic masses of $\mathrm{A}$ and $\mathrm{B}$.

Calculate the depression in the freezing point of water when $10 \mathrm{g}$ of  ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{CHClCOOH}$  is added to $250 \mathrm{g}$ of water. ${\mathrm{K}}_{\mathrm{a}}=1.4\times {10}^{-3}, {\mathrm{K}}_{\mathrm{f}}=1.86 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}$.

$19.5 \mathrm{g}$of ${\mathrm{CH}}_2\mathrm{FCOOH}$ is dissolved in $500 \mathrm{g}$ of water. The depression in the freezing point of water observed is $1.0^{°}\mathrm{C}$. Calculate the Van't Hoff factor and dissociation constant of fluoroacetic acid.

$100 \mathrm{g}$of liquid $\mathrm{A}$ (molar mass $140 \mathrm{g} {\mathrm{mol}}^{-1}$) was dissolved in $1000 \mathrm{g}$ of liquid $\mathrm{B}$ (molar mass $180 \mathrm{g} {\mathrm{mol}}^{-1}$). The vapour pressure of pure liquid $\mathrm{B}$ was found to be $500 \mathrm{torr}$. Calculate the vapour pressure of pure liquid $\mathrm{A}$ and its vapour pressure in the solution if the total vapour pressure of the solution is $475 \mathrm{Torr}$.

Determine the amount of ${\mathrm{CaCl}}_2 \left(\mathrm{i}=2.47\right)$ dissolved in $2.5$ litre of water such that its osmotic pressure is $0.75 \mathrm{atm}$at $27°\mathrm{C}$.

Determine the osmotic pressure of a solution prepared by dissolving $25 \mathrm{mg}$ of ${\mathrm{K}}_2{\mathrm{SO}}_4$ in $2$ litre of water at${25}^{\mathrm{o}}\mathrm{C}$, assuming that it is completely dissociated.

Benzene and Toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and toluene at $300 \mathrm{K}$ are $50.71 \mathrm{mm} \mathrm{Hg}$ and $32.06 \mathrm{mm} \mathrm{Hg}$ respectively. Calculate the mole fraction of benzene in vapour phase if $80 \mathrm{g}$ of benzene is mixed with $100 \mathrm{g}$ of toluene.