CBSE Class 11 Chemistry The Gas Laws Flash Cards

CBSE Class 11 Chemistry The Gas Laws Flash Cards. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Please click the link below to download pdf file of CBSE Class 11 Chemistry The Gas Laws Flash Cards.

Question. 1. The correct equation for Boyle's law is :-
(a) \( \frac{d^2P}{P} = - \frac{dV}{dT} \)
(b) \( \frac{d^2P}{P} = + \frac{d^2V}{dT} \)
(c) \( \frac{dP}{P} = - \frac{dV}{V} \)
(d) \( \frac{dP}{P} = + \frac{dV}{V} \)
Answer: C

Question. 2. Under which of the following conditions, Van der Waal's gas approaches ideal behaviour ?
(a) Extremely low pressure
(b) High pressure
(c) Low product of PV
(d) Low temperature
Answer: A

Question. 3. A gas behaves like an ideal gas under conditions of
(a) High pressure and low temperature
(b) High temperature and high pressure
(c) Low pressure and high temperature
(d) Low pressure and low temperature
Answer: C

Question. 4. When the temperature is raised, the viscosity of the liquid decreases. This is because
(a) Attraction between the molecules increases
(b) Covalent and hydrogen bond forces decrease
(c) Volume of the solution decreases
(d) Increase in temperature increases the average kinetic energy of the molecules which over-comes the attractive force between them
Answer: D

Question. 5. Which of the following gases has the lowest average speed at 25°C ?
(a) NH₃
(b) O₂
(c) CH₄
(d) H₂S
Answer: D

Question. 6. If the four tubes of a car are filled to the same pressure with N₂, O₂, H₂ and Ne separately, then which one will be filled first ?
(a) O₂
(b) H₂
(c) Ne
(d) N₂
Answer: B

Question. 7. An ideal gas expands according to PV = constant. On expansion, the temperature of gas
(a) will rise
(b) will drop
(c) will remain constant
(d) cannot be determined because the external pressure is not known
Answer: C

Question. 8. Some assumptions from the kinetic molecular theory are listed below. Which one is most frequently cited to explain Charle's law ?
(a) Collisions of gas particle are elastic and total kinetic energy of the gas is constant
(b) A gas consists of tiny particles moving in random straight line motion
(c) The volume of the particle is negligible compared to the volume of the gas
(d) The average kinetic energy of gas particles is proportional to the Kelvin temperature
Answer: D

Question. 9. Universal gas constant (R) is divided by Avogadro's number (N₀) then the value is equivalent to
(a) van der Waal's constant
(b) Rydberg's constant
(c) Planck's constant
(d) Boltzmann's constant
Answer: B

Question. 10. The term that accounts for intermolecular force in van der Waal's equation for non ideal gas is
(a) RT
(b) V – b
(c) (P + \( \alpha/V^2 \))
(d) (RT)^–1

Question. 11. According to the kinetic energy of gases, in an ideal gas, between two successive collisions a gas molecules travels
(a) in a circular path
(b) in a wavy path
(c) in a straight line path
(d) with an accelerated velocity
Answer: C

THE GAS LAWS

MATCH THE STATEMENT OF DIFFERENT GASEOUS LAW AND ITS MATHEMATICAL EXPRESSION: [4 Marks]

Answer:
1 - c - iv
2 - d - i
3 - b - iii
4 - a - ii

Teacher's Note:
a) Boyle's law connects pressure and volume inversely, matching expression iv.
b) Gay Lussac's law connects pressure and temperature directly, matching expression i.
c) Avogadro law relates volume and amount of substance, matching expression iii.
d) Charles' law relates volume and temperature directly, matching expression ii.

Fill in the blank with appropriate word given in the box.

1. A gas that follows Boyle's law, Charles' law and Avogadro law strictly is called .................... (Ideal Gas / Real Gas) [1 Mark]

Answer: Ideal Gas

Teacher's Note:
a) An ideal gas strictly obeys all gas laws under all conditions of temperature and pressure.

2. The lowest hypothetical or imaginary temperature at which gases are supposed to occupy zero .................... is called Absolute zero. (pressure / volume) [1 Mark]

Answer: volume

Teacher's Note:
a) Absolute zero corresponds to zero volume according to Charles' law extrapolation.

3. Each line of the Pressure vs. temperature (Kelvin) graph at constant molar volume is called .................... (isotherm / isobar / isochore) [1 Mark]

Answer: isochore

Teacher's Note:
a) A constant volume process or graph is termed an isochore.

4. Each line of the Volume vs. temperature (Kelvin) graph at constant pressure is called .................... (isotherm / isobar / isochore) [1 Mark]

Answer: isobar

Teacher's Note:
a) A constant pressure process or graph is termed an isobar.

5. Each line of the Pressure vs. Volume graph at constant temperature is called ............... (isotherm/ isobar/ isochore) [1 Mark]

Answer: isotherm

1. A Pressure vs. Volume graph drawn at a constant temperature is known as an isotherm.
2. Isobar represents constant pressure and isochore represents constant volume.
3. Hence, the correct term is isotherm.

Teacher's Note:
a) An isotherm is a line of constant temperature on a thermodynamic diagram.
b) Boyle's Law is graphically represented by isotherms.

6. Dalton’s Law of partial pressure states that the total pressure exerted by the mixture of ......................................... is equal to the sum of the partial pressures of individual gases. (Reacting gases/ non-reactive gases) [1 Mark]

Answer: non-reactive gases

1. Dalton's Law of partial pressures applies only to a mixture of gases that do not chemically react with each other.
2. If gases react chemically, the total pressure will change due to the formation of new substances.
3. Therefore, the blank must be filled with non-reactive gases.

Teacher's Note:
a) Non-reactive gas mixtures follow the additive pressure rule strictly.
b) Total pressure equals the sum of individual partial pressures: P_total = P_A + P_B + ...

7. At a constant temperature, pressure is ................ proportional to the density of a fixed mass of the gas.( inversely/directly) [1 Mark]

Answer: directly

1. According to the ideal gas equation, P = dRT / M.
2. At constant temperature (T) and for a fixed mass, density (d) is directly proportional to pressure (P).
3. Hence, pressure is directly proportional to density.

Teacher's Note:
a) Combining ideal gas law with density gives P / d = constant at constant T.
b) Higher pressure compresses the gas, increasing its density.

8. Kelvin scale of temperature is also called ................. of temperature and is used in all scientific works.( Thermodynamic scale/ Thermometer) [1 Mark]

Answer: Thermodynamic scale

1. The Kelvin scale is based on the laws of thermodynamics, specifically absolute zero.
2. It is universally accepted in scientific calculations and is referred to as the thermodynamic temperature scale.
3. Therefore, the correct option is Thermodynamic scale.

Teacher's Note:
a) Absolute zero (0 K) is the temperature at which molecular motion theoretically ceases.
b) It does not depend on the property of any particular substance or thermometer.

9. Pressure exerted by ........................ water vapour is called aqueous tension. (unsaturated/saturated) [1 Mark]

Answer: saturated

1. When a gas is collected over water, it becomes moist due to water vapour.
2. The pressure exerted by saturated water vapour at a given temperature is known as aqueous tension.
3. Hence, the correct term is saturated.

Teacher's Note:
a) Aqueous tension is constant at a fixed temperature for saturated vapour.
b) Dry gas pressure is calculated by subtracting aqueous tension from total pressure.

10. Gases are generally collected over water and therefore are ............ (Dry/ moist) [1 Mark]

Answer: moist

1. Gases collected over water trap water molecules in vapor form.
2. Due to the presence of water vapour, the collected gas is not dry.
3. Therefore, the gas is moist.

Teacher's Note:
a) Laboratory preparation of gases like hydrogen or oxygen involves collection over water.
b) Corrections must be applied to find the pressure of the dry gas.

THE GAS LAWS / KINETIC MOLECULAR THEORY OF GASES / REAL GAS

MULTIPLE CHOICE TYPE

1. The temperature at which a real gas obeys ideal gas law over an appreciable range of pressure is called [1 Mark]
a) Critical temperature
b) Boyle temperature
c) Inversion Temperature
d) None

Answer: (b) Boyle temperature

1. Boyle temperature (T_B) is defined as the temperature at which a real gas exhibits ideal gas behavior over a wide range of pressure.
2. At this temperature, the second virial coefficient becomes zero.
3. Hence, the correct option is (b).

Teacher's Note:
a) Real gases obey PV = nRT closely at Boyle temperature.
b) Different gases have different Boyle temperatures.

2. Which one is correctly represent the unit of Universal Gas Constant? [1 Mark]
a) bar L K^-1 mol^-1
b) L atm K^-1 mol^-1
c) J K^-1 mol^-1
d) All

Answer: (d) All

1. The value of R in bar L K^-1 mol^-1 is 0.08314.
2. The value of R in L atm K^-1 mol^-1 is 0.0821.
3. The value of R in J K^-1 mol^-1 is 8.314.
4. Since all given units are correct representations in different systems, the correct option is (d).

Teacher's Note:
a) Universal gas constant R has different numerical values depending on pressure and volume units.
b) Always check the units of P, V, and T before substituting R in equations.

3. Which one of the equation correctly represent van dar Waal equation for n mole of a real gas [1 Mark]
a) (P + a n/v²) ( V-nb) = nRT
b) ( P + a n²/v²) ( V-nb) = nRT
c) (P + a n/v²) ( V-nb) = RT
d) (P + a n/v²) ( V-b) = nRT

Answer: (b) ( P + a n²/v²) ( V-nb) = nRT

1. Pressure correction for n moles is \(\frac{an^2}{V^2}\), making corrected pressure \(P + \frac{an^2}{V^2}\).
2. Volume correction for n moles is nb, making corrected volume (V - nb).
3. Substituting into the ideal gas equation gives \(\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT\).
4. Hence, the correct option is (b).

Teacher's Note:
a) Van der Waals equation corrects for intermolecular forces and finite molecular volume.
b) Watch out for the exponent of n in the pressure correction term.

4. At which condition real gas behaves like ideal gas? [1 Mark]
a) At higher T and higher P
b) At higher T and lower P
c) At lower T and higher P
d) At lower T and lower P

Answer: (b) At higher T and lower P

1. At high temperature, kinetic energy of molecules is high, making intermolecular forces negligible.
2. At low pressure, volume of molecules is negligible compared to total volume.
3. These are the exact conditions where real gases approach ideal behavior.
4. Hence, the correct option is (b).

Teacher's Note:
a) Real gases deviate most at low temperature and high pressure.
b) Ideal gas assumptions ignore molecular volume and intermolecular attractions.

5. Kinetic energy of the gas molecules is [1 Mark]

a) Directly proportional to T²
b) Inversely proportional to T
c) Directly proportional to T
d) None of these

Answer: (c) Directly proportional to T

1. Average kinetic energy per mole of an ideal gas is given by E = \(\frac{3}{2}\) RT.
2. Kinetic energy depends only on absolute temperature (T).
3. Thus, kinetic energy is directly proportional to T.
4. Hence, the correct option is (c).

Teacher's Note:
a) Temperature is a direct measure of average translational kinetic energy.
b) At absolute zero, molecular kinetic energy becomes zero.

6. The value of compressibility factor Z for ideal gas is [1 Mark]
a) Equal to one
b) Greater than one
c) Less than one
d) None of these

Answer: (a) Equal to one

1. Compressibility factor is defined as Z = \(\frac{PV}{nRT}\).
2. For an ideal gas, PV = nRT under all conditions of temperature and pressure.
3. Therefore, Z = 1 for an ideal gas.
4. Hence, the correct option is (a).

Teacher's Note:
a) Z measures deviation from ideal gas behavior.
b) If Z > 1, repulsive forces dominate; if Z < 1, attractive forces dominate.

Question. 13. A real gas at a very high pressure occupies
(a) Less volume then that of an ideal gas under identical condition
(b) More volume than that of an ideal gas under identical conditions
(c) Same volume than that of an ideal gas under identical conditions
(d) Cannot be predicted
Answer: B

Question. 14. Temperature according to kinetic theory, is a measure of
(a) Average translational kinetic energy of gas molecules
(b) Intermolecular attraction
(c) Intermolecular distances
(d) Volume of gas
Answer: A

Question. 15. A gas deviates from ideal behaviour at a high pressure because its molecules
(a) Show the Tyndall effect
(b) Have kinetic energy
(c) Attract one another
(d) Are bound by covalent bonds
Answer: C

Question. 16. Which statement about real gases is true ?
(a) Forces of attraction and repulsion exist between gas particles as close range
(b) The behaviour of real gases can be exactly predicted using the ideal gas law
(c) The volume of the gas particle is zero
(d) The mass of the gas particles is zero
Answer: A

Question. 17. It is easier to liquefy oxygen than hydrogen because
(a) Oxygen has a higher critical temperature and a higher inversion temperature than hydrogen
(b) The critical temperature and inversion temperature of oxygen is very low
(c) Oxygen has a higher critical temperature and lower inversion temperature than hydrogen
(d) Oxygen has a lower critical temperature and higher inversion temperature than hydrogen
Answer: A