21 questions from 2022
A box contains \( 0.90 \, \text{g} \) of liquid water in equilibrium with water vapour at \( 27^\circ \mathrm{C} \). The equilibrium vapour pressure of water at \( 27^\circ \mathrm{C} \) is \( 32.0 \, \text{Torr} \). When the volume of the box is increased, some of the liquid water evaporates to maintain the equilibrium pressure. If all the liquid water evaporates, then the volume of the box must be ______ litre. [Nearest integer]
(Given: \( R = 0.082 \, \mathrm{L \, atm \, K^{-1} \, mol^{-1}} \) )
(Ignore the volume of the liquid water and assume water vapours behave as an ideal gas).
If \( \mathrm{O_2} \) gas is bubbled through water at \( 303 \, \text{K} \), the number of millimoles of \( \mathrm{O_2} \) gas that dissolve in \( 1 \) litre of water is __________. (Nearest Integer)
(Given: Henry’s Law constant for \( \mathrm{O_2} \) at \( 303 \, \text{K} \) is \( 46.82 \; k \, \text{bar} \) and partial pressure of \( \mathrm{O_2} = 0.920 \; \text{bar} \))
(Assume solubility of \( \mathrm{O_2} \) in water is too small, nearly negligible)
The osmotic pressure of blood is \( 7.47 \, \text{bar} \) at \( 300 \, \text{K} \). To inject glucose to a patient intravenously, it has to be isotonic with blood. The concentration of glucose solution in \( \text{g L}^{-1} \) is __________.
(Molar mass of glucose \( = 180 \, \text{g mol}^{-1} \), \( R = 0.083 \, \text{L bar K}^{-1} \, \text{mol}^{-1} \)) (Nearest integer)
\( 1.2 \, \text{mL} \) of acetic acid is dissolved in water to make \( 2.0 \, \text{L} \) of solution. The depression in freezing point observed for this strength of acid is \( 0.0198^\circ \text{C} \). The percentage of dissociation of the acid is ________ (Nearest integer)
[Given: Density of acetic acid is \( 1.02 \, \text{g mL}^{-1} \) ]
Molar mass of acetic acid is \( 60 \, \text{g mol}^{-1} \)
\( K_f ( \text{H}_2\text{O} ) = 1.85 \, \text{K kg mol}^{-1} \)
Two solutions A and B are prepared by dissolving \( 1 \, \mathrm{g} \) of non-volatile solutes X and Y, respectively in \( 1 \, \mathrm{kg} \) of water. The ratio of depression in freezing points for A and B is found to be \( 1:4 \). The ratio of molar masses of X and Y is:
\( 2 \, \mathrm{g} \) of a non-volatile non-electrolyte solute is dissolved in \( 200 \, \mathrm{g} \) of two different solvents A and B whose ebullioscopic constants are in the ratio of \( 1 : 8 \). The elevation in boiling points of A and B are in the ratio \( \dfrac{x}{y} \; (x : y) \). The value of \( y \) is ________ (Nearest Integer).
Boiling point of a \( 2\% \) aqueous solution of a non-volatile solute A is equal to the boiling point of \( 8\% \) aqueous solution of a non-volatile solute B. The relation between molecular weights of A and B is:
The depression in freezing point observed for a formic acid solution of concentration \( 0.5 \,\mathrm{mL \, L^{-1}} \) is \( 0.0405^\circ \mathrm{C} \). Density of formic acid is \( 1.05 \,\mathrm{g \, mL^{-1}} \). The Van’t Hoff factor of the formic acid solution is nearly : (Given for water \( k_f = 1.86 \,\mathrm{kg \, mol^{-1}} \))
A gaseous mixture of two substances A and B, under a total pressure of \( 0.8 \, \text{atm} \) is in equilibrium with an ideal liquid solution. The mole fraction of substance A is \( 0.5 \) in the vapour phase and \( 0.2 \) in the liquid phase. The vapour pressure of pure liquid A is __________ \( \text{atm} \). (Nearest integer)
\( 2.5 \, \text{g} \) of protein containing only glycine \( \left( \mathrm{C_2H_5NO_2} \right) \) is dissolved in water to make \( 500 \, \text{mL} \) of solution. The osmotic pressure of this solution at \( 300 \, \mathrm{K} \) is found to be \( 5.03 \times 10^{-3} \, \text{bar} \). The total number of glycine units present in the protein is _______________.
(Given : \( R = 0.083 \, \text{L bar K}^{-1} \, \text{mol}^{-1} \) )
Elevation in boiling point for \( 1.5 \) molal solution of glucose in water is \( 4 \, \mathrm{K} \). The depression in freezing point for \( 4.5 \) molal of glucose in water is \( 4 \, \mathrm{K} \). The ratio of molal elevation constant to molal depression constant \( \left( \frac{K_b}{K_f} \right) \) is ______.
\( 150 \, \text{g} \) of acetic acid was contaminated with \( 10.2 \, \text{g} \) ascorbic acid \( (\mathrm{C_6H_8O_6}) \) to lower down its freezing point by \( (x \times 10^{-1})^\circ \text{C} \). The value of \( x \) is __________. (Nearest integer)
Molar mas of ascorbic acid \( = 176 \, \text{g mol}^{-1} \)
A solution containing \( 2.5 \times 10^{-3} \, \mathrm{kg} \) of a solute dissolved in \( 75 \times 10^{-3} \, \mathrm{kg} \) of water boils at \( 373..535 \, \mathrm{K} \). The molar mass of the solute is _______ \( \mathrm{g\,mol^{-1}} \). [nearest integer]
\( \left( \text{Given : } K_b\,(\mathrm{H_2O}) = 0.52 \, \mathrm{K\,mol^{-1}} \text{ and boiling point of water } = 373.15 \, \mathrm{K} \right) \)
When a certain amount of solid A is dissolved in \( 100 \, \mathrm{g} \) of water at \( 25^\circ \mathrm{C} \) to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure of pure water is \( 23.76 \, \mathrm{mm \, Hg} \). The number of moles of solute A added is ________. (Nearest Integer)
A company dissolves ‘x’ amount of \( \mathrm{CO_2} \) at \( 298 \, \mathrm{K} \) in \( 1 \) litre of water to prepare soda water. \( X = \) _______ \( \times 10^{-3} \, \mathrm{g} \). (nearest integer)
(Given: partial pressure of \( \mathrm{CO_2} \) at \( 298 \, \mathrm{K} = 0.835 \, \mathrm{bar} \).
Henry’s law constant for \( \mathrm{CO_2} \) at \( 298 \, \mathrm{K} = 1.67 \, k \, \mathrm{bar} \).
Atomic mass of H, C and O is \( 1 \), \( 12 \), and \( 6 \, \mathrm{g \, mol^{-1}} \), respectively)
The elevation in boiling point for \( 1 \) molal solution of non-volatile solute A is \( 3 \, \text{K} \). The depression in freezing point for \( 2 \) molal solution of A in the same solvent is \( 6 \, \text{K} \). The ratio of \( K_b \) and \( K_f \) i.e., \( {K_b}/{K_f} \) is \( 1 : X \). The value of \( X \) is [nearest integer]
A \( 0.5 \) percent solution of potassium chloride was found to freeze at \( -0.24^\circ \mathrm{C} \). The percentage dissociation of potassium chloride is ____________ (Nearest integer).
Molal depression constant for water is \( 1.80 \, \text{K kg mol}^{-1} \) and molar mass of \( \mathrm{KCl} \) is \( 74.6 \, \text{g mol}^{-1} \).
Solute A associates in water. When \( 0.7 \, \mathrm{g} \) of solute A is dissolved in \( 42.0 \, \mathrm{g} \) of water, it depresses the freezing point by \( 0.2^{\circ}\mathrm{C} \). The percentage association of solute A in water, is:
[Given: Molar mass of A \( = 93 \, \mathrm{g \, mol^{-1}} \). Molal depression constant of water is \( 1.86 \, \mathrm{K \, kg \, mol^{-1}} \).]
\( 1.80 \, \text{g} \) of solute A was dissolved in \( 62.5 \, \text{cm}^3 \) of ethanol and freezing point of the solution was found to be \( 155.1 \, \text{K} \). The molar mass of solute A is ____ \( \text{g mol}^{-1} \).
[Given: Freezing point of ethanol is \( 156.0 \, \text{K} \). Density of ethanol is \( 0.80 \, \text{g cm}^{-3} \). Freezing point depression constant of ethanol is \( 2.00 \, \text{K kg mol}^{-1} \)]
The vapour pressures of two volatile liquids \( A \) and \( B \) at \( 25^\circ \text{C} \) are \( 50 \, \text{Torr} \) and \( 100 \, \text{Torr} \), respectively. If the liquid mixture contains \( 0.3 \) mole fraction of \( A \), then the mole fraction of liquid \( B \) in the vapour phase is \( \frac{x}{17} \). The value of \( x \) is ______.
The osmotic pressure exerted by a solution prepared by dissolving \( 2.0 \, \text{g} \) of protein of molar mass \( 60 \, \text{kg mol}^{-1} \) in \( 200 \, \text{mL} \) of water at \( 27^\circ \text{C} \) is ________ \( \text{Pa} \). [Integer value] (Use \( R = 0.083 \, \text{L} \, \text{bar} \, \text{mol}^{-1} \, \text{K}^{-1} \))
