Problem 20
Two liquids \(A\) and \(B\) have vapour pressure in the ratio \(P_{A}^{\circ}: P_{B}^{\circ}=1: 3\) at a certain temperature. Assume \(A\) and \(B\) form an ideal solution and the ratio of mole fractions of \(A\) to \(B\) in the vapour phase is \(4: 3\). Then the mole fraction of \(B\) in the solution at the same temperature is : (a) \(\frac{1}{5}\) (b) \(\frac{2}{3}\) (c) \(\frac{4}{5}\) (d) \(\frac{1}{4}\)
Problem 25
Select correct statement? (a) Heats of vaporisation for a pure solvent and for a solution are similar because similar intermolecular forces between solvent molecules must be overcome in both cases (b) Entropy change between solution and vapoür is smaller than the entropy change between pure solvent and vapour (c) Boiling point of the solution is larger than that of the pure solvent (d) All are correct statements
Problem 28
The boiling point of an azeotropic mixture of water-ethanol is less than that of both water and ethanol. Then: (a) the mixture will show negative deviation from Raoult's law (b) the mixture will show positive deviation from Raoult's law (c) the mixture will show no deviation from Raoult's law (d) this mixture cannot be considered as true solution
Problem 29
Formation of a solution from two components can be considered as : (i) Pure solvent \(\rightarrow\) separated solvent molecules, \(\Delta H_{1}\) (ii) Pure solute \(\rightarrow\) separated solute molecules, \(\Delta H_{2}\) (iii) separated solvent and solute molecules \(\rightarrow\) solution, \(\Delta H_{3}\) Solution so formed will be ideal if : (a) \(\Delta H_{\text {Soln }}=\Delta H_{1}+\Delta H_{2}+\Delta H_{3}\) (b) \(\Delta H_{\text {Soln }}=\Delta H_{1}+\Delta H_{2}-\Delta H_{3}\) (c) \(\Delta H_{\text {Soln }}=\Delta H_{1}-\Delta H_{2}-\Delta H_{3}\) (d) \(\Delta H_{\text {Soln }}=\Delta H_{3}-\Delta H_{1}-\Delta H_{2}\)
Problem 34
Total vapour pressure of mixture of 1 mole of volatile component \(A\left(P_{A}^{\circ}=100 \mathrm{~mm} \mathrm{Hg}\right.\) ) and 3 mole of volatile component \(B\left(P_{B}^{\circ}=80 \mathrm{~mm} \mathrm{Hg}\right.\) ) is \(90 \mathrm{~mm} \mathrm{Hg}\). For such case: (a) there is positive deviation from Raoult's law (b) boiling point has been lowered (c) force of attraction between \(A\) and \(B\) is smaller than that between \(A\) and \(A\) or between \(B\) and \(B\) (d) all the above statements are correct
Problem 37
An azeotropic mixture of two liquids has a boiling point higher than either of them when it: (a) shows positive deviation from Raoult's law (b) shows negative deviation from Raoult's law (c) shows ideal behaviour (d) is saturated
Problem 38
If two liquids \(A\left(P_{A}^{\circ}=100\right.\) torr \()\) and \(B\left(P_{B}^{\circ}=200\right.\) torr \()\) are completely immiscible with each other (each one will behave independently of the other) are present in a closed vessel. The total vapour pressure of the system will be: (a) less than 100 torr (b) greater than 200 torr (c) between 100 to 200 torr (d) 300 torr
Problem 39
When a liquid that is immiscible with water was steam distilled at \(95.2^{\circ} \mathrm{C}\) at a total pressure of 748 torr, the distillate contained \(1.25 \mathrm{~g}\) of the liquid per gram of water. The vapour pressure of water is 648 torr at \(95.2^{\circ} \mathrm{C}\), what is the molar mass of liquid? (a) \(7.975 \mathrm{~g} / \mathrm{mol}\) (b) \(166 \mathrm{~g} / \mathrm{mol}\) (c) \(145.8 \mathrm{~g} / \mathrm{mol}\) (d) None of these
Problem 44
The van't Hoff factor \(i\) for an electrolyte which undergoes dissociation and association in solvent are respectively: (a) greater than one and less than one (b) less than one and greater than one (c) less than one and less than one (d) greater than one and greater than one
Problem 46
An aqueous solution is \(1.00\) molal in KI. Which change will cause the vapour pressure of the solution to increase ? (a) addition of water (b) addition of \(\mathrm{NaCl}\) (c) addition of \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) (d) Addition of \(1.0\) molal KI
