Solutions

A 0.5 percent solution of potassium chloride was found to freeze at $-0.24$°C. The percentage dissociation of potassium chloride is ______. (Nearest integer)

(Molal depression constant for water is 1.80 K kg mol$^{-1}$ and molar mass of KCl is 74.6 g mol$^{-1}$)

The osmotic pressure exerted by a solution prepared by dissolving 2.0 g of protein of molar mass 60 kg mol$^{-1}$ in 200 mL of water at 27°C is ______ Pa. [integer value]

(use $R=0.083$ L bar mol$^{-1}$ K$^{-1}$)

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : At 10°C, the density of a 5 M solution of KCl [atomic masses of K & Cl are 39 & 35.5 g mol$^{-1}$ respectively], is '$x$' g ml$^{-1}$. The solution is cooled to $-21$°C. The molality of the solution will remain unchanged.

Reason (R) : The molality of a solution does not change with temperature as mass remains unaffected with temperature.

In the light of the above statements, choose the correct answer from the options given below.

2 g of a non-volatile non-electrolyte solute is disolved in 200 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 $\dfrac xy$ $(x:y)$. The value of $y$ is ______. (Nearest Integer)

A solution containing $2.5\times10^{-3}$ kg of a solute dissolved in $75\times10^{-3}$ kg of water boils at 373.535 K. The molar mass of the solute is ______ g mol$^{-1}$. [nearest integer] (Given : $K_b(\mathrm{H_2O})=0.52$ K kg mol$^{-1}$ and boiling point of water = 373.15 K)

The vapour pressures of two volatile liquids A and B at 25°C are 50 Torr and 100 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 ______.

2.5 g of protein containing only glycine ($\mathrm{C_2H_5NO_2}$) is dissolved in water to make 500 mL of solution. The osmotic pressure of this solution at 300 K is found to be $5.03\times10^{-3}$ bar. The total number of glycine units present in the protein is ______.

(Given : R = 0.083 L bar K$^{-1}$ mol$^{-1}$)

1.2 mL of acetic acid is dissolved in water to make 2.0 L of solution. The depression in freezing point observed for this strength of acid is 0.0198°C. The percentage of dissociation of the acid is ______. (Nearest integer)

[Given : Density of acetic acid is 1.02 g mL$^{-1}$; Molar mass of acetic acid is 60 g mol$^{-1}$; $K_f(\mathrm{H_2O})=1.85$ K kg mol$^{-1}$]

A box contains 0.90 g of liquid water in equilibrium with water vapour at 27°C. The equilibrium vapour pressure of water at 27°C is 32.0 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 L atm K$^{-1}$ mol$^{-1}$)

(Ignore the volume of the liquid water and assume water vapours behave as an ideal gas.)

Elevation in boiling point for 1.5 molal solution of glucose in water is 4 K. The depression in freezing point for 4.5 molal solution of glucose in water is 4 K. The ratio of molal elevation constant to molal depression constant ($K_b/K_f$) is ______.

For a solution of the gases A, B, C and D in water at 298 K, the values of Henry's law constant ($K_H$) are 30.40, 2.34, $1.56\times10^{-5}$ and 0.513 k bar respectively. In the given graph, the lines marked as 'p' and 's' correspond respectively to :

The depression in freezing point observed for a formic acid solution of concentration 0.5 mL L$^{-1}$ is 0.0405°C. Density of formic acid is 1.05 g mL$^{-1}$. The Van't Hoff factor of the formic acid solution is nearly : (Given for water $k_f=1.86$ k kg mol$^{-1}$)

Two solutions A and B are prepared by dissolving 1 g of non-volatile solutes X and Y, respectively in 1 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

The elevation in boiling point for 1 molal solution of non-volatile solute A is 3 K. The depression in freezing point for 2 molal solution of A in the same solvent is 6 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]

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

When a certain amount of solid A is dissolved in 100 g of water at 25°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 mmHg. The number of moles of solute A added is ______. (Nearest Integer)

150 g of acetic acid was contaminated with 10.2 g ascorbic acid $(\mathrm{C_6H_8O_6})$ to lower down its freezing point by $(x\times10^{-1})$°C. The value of $x$ is ______. (Nearest integer)

[Given $K_f$ = 3.9 K kg mol$^{-1}$; molar mass of ascorbic acid = 176 g mol$^{-1}$]

A gaseous mixture of two substances A and B, under a total pressure of 0.8 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 ______ atm. (Nearest integer)

If O$_2$ gas is bubbled through water at 303 K, the number of millimoles of O$_2$ gas that dissolve in 1 litre of water is _______. (Nearest Integer)

(Given : Henry's Law constant for O$_2$ at 303 K is 46.82 k bar and partial pressure of O$_2$ = 0.920 bar)

(Assume solubility of O$_2$ in water is too small, nearly negligible)

1.80 g of solute A was dissolved in 62.5 cm$^3$ of ethanol and freezing point of the solution was found to be 155.1 K. The molar mass of solute A is _______ g mol$^{-1}$.

[Given: Freezing point of ethanol is 156.0 K. Density of ethanol is 0.80 g cm$^{-3}$. Freezing point depression constant of ethanol is 2.00 K kg mol$^{-1}$]