Vapour Pressure

Q.

Which of the assumption of the kinetic - molecular theory best explains Daltons law of partial pressure?

1. Gas molecules move at random with no attractive forces between them.

2. The velocity of gas molecules is proportional to their kelvin temperature.

3. Collisions with the walls of the container or with other molecules are elastic.

4. The amount of space occupied by a gas is much greater than the space occupied by the actual gas molecules.

Q. The vapour pressure of a dilute aqueous solution of glucose is $750\text{mm Hg}$ at $373\text{K}$. Calculate:
$\left(i\right)$ Molality
$\left(ii\right)$ Mole fraction of the solute

1. $\left(i\right)0.013\text{m},\left(ii\right)0.74$
2. $\left(i\right)0.74\text{m},\left(ii\right)0.0132$
3. $\left(i\right)0.74\text{m},\left(ii\right)0.98$
4. $\left(i\right)0.013\text{m},\left(ii\right)0.26$

Q.

Equilibrium vapour pressure or saturated vapour pressure: Vapour pressure in the state of equilibrium between liquid phase and vapour phase.

What does it mean ?

Q.

A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.

a) What is the initial effect of the change on vapour pressure?

b) How do rates of evaporation and condensation change initially?

c) What happens when equilibrium is restored finally and what will be the final vapour pressure?

Q. 7 A specimen of air at 298K and 750mmofHg saturated with benzene at 298K and 100mmofHg if the 1/3 volume of initial volume compress isothermally so found the final pressure of the system 1)2250torr 2)2150torr 3)2050torr 4)1950torr

Q. At ${80}^{\circ }\text{C}$, the vapour pressure of a pure liquid $A$ is $520\text{mm Hg}$ and that of a pure liquid of $B$ is $1000\text{mm Hg}$. If the ideal mixture of liquids $A$ and $B$ boils at ${80}^{\circ }\text{C}$ and 1 atm pressure, the amount of solution A in the mixture is: (1 atm = 760 mm Hg)

1. $50\text{mol}\%$
2. $52\text{mol}\%$
3. $34\text{mol}\%$
4. $48\text{mol}\%$

Q.

A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.

a) What is the initial effect of the change on vapour pressure?

b) How do rates of evaporation and condensation change initially?

c) What happens when equilibrium is restored finally and what will be the final vapour pressure?

Q. A $22.4L$ glass bulb has a total pressure of $760torr$ at $0^{\circ }C$ and contains three different gases,
nitrogen, helium and argon. If the partial pressure of nitrogen is $250torr$and the partial pressure
of argon is $130torr$ .
Given $R=62.363L.torr.mo{l}^{-1}{K}^{-1}$
Then the number of moles of helium in the bulb will be

1. 1
2. 1.5
3. 2.5
4. 0.5

Q.

before opening d bottle of ammonia , it is cooled. gve reasons.

Q. what is reduction? What does the statement "Temperature of a system is reduced to average kinetic energy of molecules" mean?

Q.

Respected authorities in this questionQuestion 7.1:

A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.

a) What is the initial effect of the change on vapour pressure?

b) How do rates of evaporation and condensation change initially?

c) What happens when equilibrium is restored finally and what will be the final vapour pressure?

Answer:

(a) If the volume of the container is suddenly increased, then the vapour pressure would decrease initially. This is because the amount of vapour remains the same, but the volume increases suddenly. As a result, the same amount of vapour is distributed in a larger volume.

(b) Since the temperature is constant, the rate of evaporation also remains constant. When the volume of the container is increased, the density of the vapour phase decreases. As a result, the rate of collisions of the vapour particles also decreases. Hence, the rate of condensation decreases initially.

(c) When equilibrium is restored finally, the rate of evaporation becomes equal to the rate of condensation. In this case, only the volume changes while the temperature remains constant. The vapour pressure depends on temperature and not on volume. Hence, the final vapour pressure will be equal to the original vapour pressure of the system.

How can the final and initial pressure be equal?

Q. A set of solutions is prepared using $180g$ of water as a solvent and $10g$ of different non-volatile solutes $A,BandC$. The relative lowering of vapour pressure in the presence of these solutes are in the order [Given, molar mass of $A=100gmo{1}^{-1};B=200gmo{l}^{-1};C=10,000gmo{l}^{-1}]$
(JEE MAIN 2020)

1. $B>C>A$
2. $C>B>A$
3. $A>B>C$
4. $A>C>B$

Q. At ${80}^{\circ }\text{C}$, the vapour pressure of a pure liquid $A$ is $520\text{mm Hg}$ and that of a pure liquid of $B$ is $1000\text{mm Hg}$. If the ideal mixture of liquids $A$ and $B$ boils at ${80}^{\circ }\text{C}$ and 1 atm pressure, the amount of solution A in the mixture is: (1 atm = 760 mm Hg)

1. $50\text{mol}\%$
2. $52\text{mol}\%$
3. $34\text{mol}\%$
4. $48\text{mol}\%$

Q. Which of the following statement is correct?

1. At a particular temperature, when vapour pressure of a liquid is less than that of atmospheric pressure, boiling point is reached.
2. Higher the vapour pressure of the liquid at a particular temperature , lower is the boiling point.
3. All of the above.
4. Higher the vapour pressure at a particular temperature, lesser the tendency for the molecules to escape easily from the surface