Vapour Pressure

Q.

At $300\mathrm{K}$ the vapour pressure of a solution containing $1$ mole of n-hexane and $3$ moles of n-heptane is $550$ mm of $\mathrm{Hg}$. At the same temperature, if one more mole of n-heptane is added to this solution, the vapour pressure of this solution increases by $10$ mm of $\mathrm{Hg}$. What is the vapour pressure in $\mathrm{mm}$ of $\mathrm{Hg}$ of n-heptane in its pure state?

Q.

Why is the vapour pressure of an aqueous solution of glucose lower than that of water

Q.

A hard substance melts at high temperature and is an insulator in both solid and molten state. This solid is most likely to be a/an:

1. Metallic Solid

2. Covalent Solid

3. Ionic Solid

4. Molecular Solid

Q. Using method of dimension, derive an expression for rate of flow(V) of a liquid through a pipe of radius(r) under a pressure gradient (p/l).Given that V also depend on coefficient of viscocity(*) of the liquid.

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. The vapour pressures of pure liquids 'A' and 'B' are $300$ and $800\text{torr}$ respectively at $25{}^{\circ }\text{C}$. When these two liquids are mixed at this temperature to form a solution in which mole fraction of 'B' is $0.92$, then the total vapour pressure is observed to be $0.95\text{atm}$. Which of the following is true for this solution?

1. $\Delta V_{\text{mix}}>0$
2. $\Delta H_{\text{mix}}<0$
3. $\Delta V_{\text{mix}}=0$
4. $\Delta H_{\text{mix}}=0$

Q. Obtain by the method of dimensional analysis an expression for the surface tension of a liquid rising in a capillary tube .assume that surface tension depends on mass m of the liquid, pressure p of the liquid and radius r of the capillary tube. The constant K =12.

Q. At high attitude the boiling point of water lowers because

1. Atmospheric pressure is high
2. Atmospheric pressure is low
3. Temperature is low
4. None of the above

Q. capillary tube of radius r is immersed in a liquid and mass of liquid, which rises in up in it is M. If the radius of the tube is doubled, then the mass of liquid which will rise in capillary tube will be A. M/2 B. M C. 2M D. M/4

Q.

Which of the following will increase with increase in temperature?

1. Molality

2. Surface tension

3. Viscosity

4. Vapor pressure

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. The highest number of allotropes are shown by:

1. Oxygen
2. Sulphur
3. Selenium
4. Tellurium

Q. Arrange the following according to the freezing point order of glucose solution 1%, 2%, 3%, 10%

Q.

An ideal solution of two liquids A and B is placed in a cylinder containing piston. Piston is pulled out isothermally so that the volume of the liquid decreases but that of vapours increases. Negligibly small amount of liquid was left and mole fraction of A in vapour is 0.4. If $P_A^0=0.4$atm and $P_B^0=1.2$atm at the experimental temperature, which of the following is the total pressure at which the liquid is almost evaporated?

1. 0.334atm

2. 0.667atm

3. 1atm

4. 2atm

Q. What is Raoults FIRST Law of relative lowering of vapour pressure? What is Raoults SECOND Law of relative lowering of vapour pressure?

Q.

Bernoullis theorem is important in the field of

Q.

Pressure exerted by saturated water vapour is called aqueous tension. What correction term will you apply to the total pressure to obtain pressure of dry gas?

Q.

In Polar molecular solids Most of them are gases or liquids at room temperature and pressure. Then my qustion is why are we calling that a Solid , if it is seen in gas or liquid

Q. The initial volume of a gas cylinder is 750.0 mL. If the pressure of gas inside the cylinder changes from 840.0 mm Hg to 360.0 mm Hg, the final volume the gas will be :

1. 1.750 L
2. 3.60 L
3. 4.032 L
4. 7.50 L

Q.

Question 43
Why is the vapour pressure of an aqueous solution of glucose lower than that of water?

Q. Describe the concept of Relative lowering of vapour pressure and elevation in boiling point in detail with suitable diagram.

Q. The equilibrium vapour pressure of water vapour over a 0.20 mole sample of liquid water is 35 torr at ${27}^{\circ }\text{C}$. If the amount of the liquid water is decreased to 0.10 mole, the equilibrium vapour pressure of it would be

1. 17.5 torr
2. 51.5 torr
3. None of these
4. 35.0 torr

Q. A liquid cannot be compressed because it has a fixed volume.

1. Either
2. True
3. False
4. Neither

Q. (a) 30 g of urea (m = 60 g $mo{l}^{-1}$) is dissolved in 846 g of water. Calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23.8 mm Hg.
(b) Write two differences betwen ideal solutions and non- ideal solutions.

Q. At 300 K, the vapour pressure of an ideal solution containing 3 mol of A and 2 mol of B is 600 torr. At the same temperature, if 1.5 mol of A and 0.5 mol of C (non-volatile) are added to this solution, the vapour pressure of solution increases by 30 torr. What is the value of $P_B^0$ (in torr)?

1. 940
2. 405
3. 90
4. None of these

Q.

In the following question a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below in each question.

Assertion (A) The temperature at which vapour pressure of a liquid is equal to the external pressure is called boiling temperature.

Reason (R) At high altitude atmospheric pressure is high.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is the correct explanation of A

(c) A is true but R is false

(d) A is false but R is true.

Q.

Give two reasons to justify:

1. Water at room temperature is liquid.
2. An iron almirah is solid at room temperature

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. With increase in temperature, viscosity and surface tension of a liquid respectively:

1. Decrease, decrease
2. Decrease, increase
3. Increase, decrease
4. Increase, increase

Q. Increase in kinetic energy can overcome intermolecular forces of attraction. How will the viscosity of liquid be affected by the increase in temperature?

1. Increase
2. No effect
3. Decrease
4. No regular pattern will be followed