Evaporation

Q. Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces between the particles. Following are the critical temperatures of some gases.

Gases	$H_2$	$He$	$O_2$	$N_2$
Critical temperature $\left(K\right)$	$33.2$	$5.3$	$154.3$	$126$

From the above data what would be the order of liquefaction of these gases? Start writing the order from the gas liquefying first.

1. $N_2,O_2,He,H_2$
2. $O_2,N_2,H_2,He$
3. $H_2,He,O_2,N_2$
4. $He,O_2,H_2,N_2$

Q. 109.The work done by a thermodynamic system in the process A-B-C is 30 j and heat absorbed by the system in the same process is 4j The change in internal energy in the process is

Q.

Boiling does not occur when:

1. Liquid is very concentrated

2. Liquid is heated in a closed vessel

3. Liquid is not very dense

4. Liquid is heated in an open vessel

Q. The mixing of gases is generally accompanied by

1. Decrease in Entropy

2. Decrease in Gibb's Energy

3. Change in heat content

4. Increase in Gibb's Energy

Q.

The property of a liquid that increases with a increase in temperature is:

1. Viscosity

2. Vapour pressure

3. Surface tension

4. Both Viscosity and Surface tension

Q. Compressibility factor, $Z$, of a gas is given as $Z=\frac{pV}{nRT}$

A What is the value of $Z$ for an ideal gas?

B For real gas what will be the effect on the value of $Z$ above Boyle’s temperature?

Q. Which of the following statement(s) is/are correct?

1. In steam distillation, organic liquid which has a higher B.P. than water​ can be boiled (distilled) at a much lower temperature
2. At equilibrium,
   $\text{Rate of dissolution}\ne \text{Rate of crystallisation}$
3. At equilibrium,
   $\text{Rate of dissolution = Rate of crystallisation}$
4. At equilibrium, the concentration ​of solute in solution will remain ​constant

Q.

Is evaporation slow process or fast?

Q.

Give an example of evaporation from daily life.

Q. Assertion $\left(A\right)$ : Gases do not liquefy above their critical temperature, even on applying high pressure.

Reason $\left(R\right)$ : Above critical temperature, the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed.

1. $A$ is true but $R$ is false.
2. Both $A$ and $R$ are true, and $R$ is the correct explanation of $A$.
3. $A$ is false but $R$ is true.
4. Both $A$ and $R$ are true, but $R$ is not the correct explanation of $A$.

Q. For real gases the relation between $p,V$ and $T$ is given by the Van der Waals equation:

$(P+\frac{a{n}^2}{V^2})(V–nb)=nRT$

where ${}^{\prime }{a}^{\prime }$ and ${}^{\prime }{b}^{\prime }$ are van der Waals constants, ${}^{\prime }n{b}^{\prime }$ is approximately equal to the total volume of the molecules of a gas. ${}^{\prime }{a}^{\prime }$ is the measure of the magnitude of intermolecular attraction.

A Arrange the following gases in the increasing order of ${}^{\prime }{b}^{\prime }$. Give a reason. $O_2,C{O}_2,H_2,He$.

B Arrange the following gases in the decreasing order of magnitude of ${}^{\prime }{a}^{\prime }$. Give a reason. $C{H}_4,O_2,H_2$

Q. During evaporation, the molecules present at the top and the bottom of a liquid escape at the same time.

1. False
2. True

Q.

define vapour pressure

Q.

The boiling points of a liquid rises on increasing pressure. Give reason

Q. During evaporation, the molecules in liquids must have sufficient energy to overcome intermolecular forces of attraction.

1. kinetic
2. potential
3. chemical

Q. You have been given a powdered mixture of carbon, sulphur and potassium chloride. How will you separate each constituent from the mixture?

1. Solvent extraction, solvent extraction, evaporation
2. Solvent extraction, solvent extraction, filtration
3. Evaporation, solvent extraction, filtration
4. Evaporation, filtration, solvent extraction

Q. 43.What is relation between mole fraction and vapourisation when solution taken in a beaker

Q. Evaporation is a spontaneous process.

1. True
2. False

Q. To separate mud from muddy water we can use filtration. The mud collected in the filter paper is known as _________.

1. filtrate
2. residue
3. crystals
4. mixture

Q. liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased. b)How do rates of evaporation and condensation change initially?

Q. How do rates of evaporation and condensation change initially?

Q. write on molecular basis the origin of latent heat of fusion?

Q.

1. Sugar
2. Sand
3. Both sugar and sand
4. Water

Q. Explain oil drop experiment by diagram ??

Q. 21.An open flask contains air at 27^° C.To what temperature it must be heated to expel one fourth of the air?

Q. Why is in water 1 litre of water is equal to 1 kilogram of water?

Q.

Statement 1: Evaporation causes cooling of the liquid

Statement 2: During evaporation, the surface molecules with high kinetic energy get evaporated.

1. Statement 1 and Statement 2 both are correct and Statement 2 is correct explanation of Statement 1.
2. Statement 1 and Statement 2 both are correct and statement 2 is not the correct explanation of statement 1.
3. Statement 1 is correct and Statement 2 is wrong.
4. Statement 2 is correct and Statement 1 is wrong.

Q. Which type of interparticle forces are broken in each of the following processes? i HCl(l) → HCl(g) ii Sublimation of dry ice iii Evaporation of water iv vaporization of ammonia