271.
A solution containing $$0.85\,g$$ of $$ZnC{l_2}$$ in $$125.0\,g$$ of water freezes at $$ - {0.23^ \circ }C.$$ The apparent degree of dissociation of the salt is ( $${K_f}$$ for water $$ = 1.86K\,kg\,mo{l^{ - 1}},$$ atomic mass : $$Zn = 65.3$$ and $$Cl = 35.5$$ )
272.
$$12\,g$$ of a nonvolatile solute dissolved in $$108\,g$$ of water produces the relative lowering of vapour pressure of $$0.1.$$ The molecular mass of the solute is :
273.
Ethylene glycol is used as an antifreeze in a cold climate. Mass of ethylene glycol which should be added to $$4 kg$$ of water to prevent it from freezing at $$ - {6^ \circ }C$$ will be : ( $${K_f}$$ for water = $$1.86\,K\,kg\,mo{l^{ - 1}},$$ and molar mass of ethylene glycol = $$62\,g\,mo{l^{ - 1}}$$ )
\[\begin{align}
& \text{Given}\,{{K}_{f}}=1.86\,K\,kg\,mo{{l}^{-1}} \\
& \Delta {{T}_{f}}=0-\left( -6 \right)={{6}^{\circ }}C \\
& \text{As we know that} \\
& \Delta {{T}_{f}}={{K}_{f}}\times \text{molality} \\
& \text{=}\frac{{{K}_{f}}\times 1000\times \text{mass of solute}}{\begin{align}
& \text{molar mass of}\,\text{solute }\times \text{ mass of solvent in kg} \\
& \text{ }\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \\
\end{align}} \\
& \text{Substituting given values in formula} \\
& 6=\frac{1.86\times 1000\times w}{62\times 4};\,w=0.8\,kg=800\,gm \\
& \\
\end{align}\]
274.
At $$760\,torr$$ pressure and $${20^ \circ }C$$ temperature, $$1\,L$$ of water dissolves $$0.04\,gm$$ of pure oxygen or $$0.02\,gm$$ of pure nitrogen. Assuming that dry air is composed of $$20\% $$ oxygen and $$80\% $$ nitrogen
(by volume), the masses ( in $$g/L$$ ) of oxygen and nitrogen dissolved by $$1\,L$$ of water at $${20^ \circ }C$$ exposed to air at a total pressure of $$760\,torr$$ are respectively :
275.
$$18\,g$$ of glucose $$\left( {{C_6}{H_{12}}{O_6}} \right)$$ is added to $$178.2 \,g$$ of water. The vapour pressure of water for this aqueous solution at $${100^ \circ }C$$ is
276.
The difference between the boiling point and freezing point of an aqueous solution containing sucrose ( molecular $$wt = 342\,g\,mol{e^{ - 1}}$$ ) in $$100\,g$$ of water is $${105^ \circ }C.$$ If $${K_f}$$ and $${K_b}$$ of water are $$1.86$$ and $$0.51\,K\,kg\,mo{l^{ - 1}}$$ respectively, the weight of sucrose in the solution is about
At high altitudes, the partial pressure of oxygen is less than that at the ground level. This leads to low concentrations of oxygen in the blood and tissues of people living at high altitudes or climbers. Low blood oxygen causes climbers to become weak and unable to think clearly, symptoms of a condition known as anoxia.
278.
How much oxygen is dissolved in $$100\,mL$$ water at $$298\,K$$ if partial pressure of oxygen is $$0.5\,atm$$ and $${K_H} = 1.4 \times {10^{ - 3}}\,mol/L/atm?$$