Gaseous and Liquid States NIOS Intext Questions With Answer
National Institute of Open Schooling (NIOS)
Sr. Secondary, Module-2
Lession-5: Gaseous and Liquid States NIOS Intext Questions With Answer
INTEXT QUESTIONS 5.1
1. The density of a gas is usually less than that of the liquid. Explain.
Answer: The density of the gas is less than that of liquid because intermolecular distances are more in gas than that of liquid molecules. Hence, more intermolecular distances means less density2. Calculate the pressure (atm) required to compress 500 mL of gas at 0.20 atm into a volume of 10 mL.
Answer: Given-P1 = 0.20atm, V1 = 500mL and V2 = 10mL
we have to calculate P1.
We know that P1V1 = P2V2
From this equation we can calculate easily the value of P2.
P2 = 10 atm.
3. Equal volumes of oxygen gas and an unknown gas weigh 2.00 and 1.75 g respectively under the same experimental conditions. What is the molar mass of the unknown gas?
Answer: Molar mass of unknown gas = (1.75 x 32)/2.00 = 28 g mol–1The molar mass of the unknown gas was found to be 28g/mol and the unknown gas is nitrogen gas N2
4. What type of intermolecular interactions are present in
a. Ne gas
b. Carbon monoxide.
Answer: a. Dispersion or London Forcesb. dipole-dipole interactions and dispersion forces.
INTEXT QUESTIONS 5.2
1. What is the difference between diffusion and effusion.
Answer: Movement of gas molecules through another gas is called diffusion.When gas escapes from a container through a very small opening it is called effusion.
2. Explain why Daltons’ law is not applicable to a system of ammonia and hydrogen chloride gas.
Answer: Ammonia and hydrogen chloride gases are reacting gases and Dalton's Law is applicable to mixture of non-reacting gases.3. The rates of diffusion of CO2 and O3 were found to be 0.29 and 0.271. What is the molecular mass of O3 if the molecular mass of CO2 is 44.
Answer: Given-rO3 = 0.271
rCO2 = 0.290
MCO2 = 44 MO3 = ?
rO3 / rCO2 = (MCO2 / MO3)1/2
squiring both sides in the above equation and putting the value we get-
Molecular mass of (MO3) = (44 x 0.29 x 0.29) / (0.271 x 0.271) = 50.4
4. Calculate the pressure exerted by 5.0 mol of carbon dioxide in a 1 litre flask at 47ºC using ideal gas equation.
Answer: By ideal gas equationpV = nRT
Putting the value we get-
p × 1.0 = (5.0 mol) (0.0821 L atm K–1 mol–1) 320 K
or, p = 131.3 atm.
INTEXT QUESTIONS 5.3
1. What are the conditions under which real gases behave as ideal gas.
Answer: At low pressure and high temperature, real gas behaves as an ideal gas2. Which term in van der waals equation accounts for the molecular volume.
Answer: Vander Waal constant 'b'3. Calculate the root mean square velocity of ozone kept in a closed vessel at 20ºC and 1 atm pressure.
Answer: 390.3 m/s.4. What is compressibility factor.
Answer: The ratio of a gas's molar volume to that of an ideal gas at constant temperature and pressure is known as the compressibility factor (Z), sometimes known as the compression factor.The compressibility factor for an ideal gas is unity, which is typically written as Z = PV/RT.
INTEXT QUESTIONS 5.4
1. Match the following.
Column I Column I i. Liquids have a definite volume
A. The molecules in a liquid can move about ii. Liquids acquire the shape of their container
B. The molecules in liquids are close and have very little free space iii. Liquids are largely incompressible
C. The inter molecular forces liquids strong enough to keep the molecules moving with in a definite space
Answer: i.C| Column I | Column I |
|---|---|
| i. Liquids have a definite volume | A. The molecules in a liquid can move about |
| ii. Liquids acquire the shape of their container | B. The molecules in liquids are close and have very little free space |
| iii. Liquids are largely incompressible | C. The inter molecular forces liquids strong enough to keep the molecules moving with in a definite space |
ii. A
III. B
2. When a liquid is heated till it starts boiling.
i. What are the small bubbles that appears initially at the bottom and
sides of the vessel made up of?
ii. What are the large bubbles that form in the boiling liquid made up
of?
Answer: i. Airii. Liquid
3. Liquids A, B and C boil at 65ºC, 120ºC and 90ºC respectively. Arrange them in the decreasing order of the strength of intermolecular forces.
Answer: B > C > AINTEXT QUESTIONS 5.5
1. Fill in the blanks.
i. A molecule at the surface of a liquid has ............... energy than the
one within the liquid.
ii. Surface tension of liquid .................... on cooling.
iii. Meniscus of a non-wetting liquid is ............... in shape while that of
a wetting liquid is ..................... in shape.
iv. When one end of a glass capillary tube was dipped in a liquid, the level of liquid inside the capillary was observed to fall. The adhesive forces in this liquid are ................. than the cohesive forces between
the liquid and glass.
v. Liquid X is more viscous than liquid Y. The intermolecular forces in Y are ................... than in X.
Answer: i. moreii. increases
iii. convex; concave
iv. stronger
v. weaker
2. What are the SI units of
i. Surface tension.
ii. Coefficient of viscosity
Answer: i. N m–1ii. N m–2s
