Evaporation

Q. Warm Water freezes faster than cold water. Why?

Q.

The vapour pressure of water at 20 degree celsius is 17.54 mmHg. What will be the vapour pressure of the water in the apparatus shown after the piston is lowered, decreasing the volume of the gas above the liquid to one half of its initial volume (assume temperature constant).

A) 8.77 mmHg

B)17.54mmHg

C)35.08 mmHg

D) between 8.77 and 17.54mmHg

Q.

Two liquids x and y boil at 110 degrees and 130 degrees Celsius respectively. Which one of them has higher vapour pressure at 50 degree Celsius? Why?

Q.

Evaporation produces cooling. Comment on the following statement.

Q. For a mixture of two volatile, completely miscible liquids A and B, with $P_A^0=500$ torr and $P_B^0=800$ torr. What is the composition of last of liquid remaining in equilibrium with vapour?
Provided the initial ideal solution has a composition of $x_A=0.6$ and $x_B=0.4$, where $x_A\text{and}{x}_B$ are the mole fraction of $A$ and $B$ respectively

1. $x_B=0.7$
2. $x_B=0.3$
3. $x_A=0.7$
4. $x_A=0.3$

Q. Gases possess characteristic critical temperature which depends upon the magnitude of intermolecular forces between the gas particles. Critical temperatures of ammonia and carbon dioxide are $405.5K$ and $304.10K$ respectively. Which of these gases will liquify first when you start cooling from $500K$ to their critical temperature?

Q. Evaporation is a spontaneous process.

1. True
2. False

Q.

We feel relief under a fan when we are perspiring. Explain, why?

Q.

Why do people feel a cooling sensation when they sit under a moving fan after sweating?

Q. Statement 1:The ionic radii of the cation is always smaller than its respective neutral atom.
Statement 2: The ionic radii of an anion is always greater than its respective neutral atom.

1. Statement 1 is wrong but Statement 2 is correct
2. Both are wrong
   
3. Both are correct
4. Statement 1 is correct but Statement 2 is wrong,

Q.

When the surface molecules with high kinetic energy escape out of liquid surface, the temperature of the liquid.

1. increases
2. decreases
3. remains the same

Q.

How is the behavior of water as a heat sink?

Q.

Water kept in an earthen pitcher, during summer days becomes very cold due to

1. condensation

2. evaporation

3. freezing

4. fusion

Q.

Particles of gas are moving with high speeds in all the directions and thus have the highest thermal energy.

1. True
2. False

Q. 60 Why boiling is not possible when liquid is heated in closed vessel?

Q. Sweating is a cooling mechanism for our body.

1. True
2. False

Q. Evaporation is a spontaneous process.

1. True
2. False

Q. Water evaporates only on heating.

1. True
2. False

Q. Assertion :During evaportaion of liquid the temperature of the liquid remains unaffected. Reason: Kinetic energy of the molecules is directly proportional to absolute temperature.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Assertion is incorrect but Reason is correct

Q.

Under what conditions can ideal gases be liquefied? Give reasons to support your answer.

Q. At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is __________.

1. equal to the rate of crystallization
   
2. zero
3. less than the rate of crystallization
   
4. greater than the rate of crystallisation
   

Q. Water vapours have more energy than water at same temperature.

Q. a gas in an open container is heated from 27^° C to 127^° C. The fraction of the original amount of gas remaining in the container will be.

Q.

When we sweat a lot and feel hot, we switch on the fan. we immediately feel cool. what is the reason? what happened to the Sweat?

Q. Cations are formed when an electron is added to a neutal atom and anions are formed when an electron is removed from a neutral atom.

Q. Why boiling point is inversely related to pressure?

Q. The osmotic pressure of a solution at $0^{\circ }C$ is $4atm$. What will be its osmotic pressure at $546K$ under similar conditions?

1. $2atm$
2. $6atm$
3. $8atm$
4. $4atm$

Q. What happens to the rate of evaporation of water, if the atmospheric pressure is increased during the extraction of the colored component from liquid?

1. Increases
2. None
3. Do not change
4. Decreases

Q. Warming ammonium chloride with sodium hydroxide in a test tube is an example of:

1. isolated system
2. open system
3. none of these
4. closed system

Q.

Water regulates ________________________ of our body.