21 + Interview Questions in Kinetic Theory in Physics – Class 11 Page 1 InterviewSolution

1.	What is the ratio of specific heats for a monatomic gas?(a) 5/3(b) 5/2(c) 7/5(d) 9/5This question was posed to me in exam.My question is based upon Kinetic Theory in section Kinetic Theory of Physics – Class 11
Answer» Right ANSWER is (a) 5/3 The explanation: The VALUE of Cv for a monatomic GAS is 3/2 R and CP is 5/2 R. Thus the value of γ is: CP/CV= 5/3.

Discussion

2.	Boyle’s law can be deduced from kinetic theory. True or False?(a) True(b) FalseThis question was addressed to me in class test.My question is from Kinetic Theory of an Ideal Gas topic in section Kinetic Theory of Physics – Class 11
Answer» Right CHOICE is (a) True To explain I would SAY: From the KINETIC theory we GET: PV=(1/3)mNvrms^2.Vrms^2 depends only on TEMPERATURE.So, if temperature is constant PV will be constant, which is Boyle’s law.

Discussion

3.	What is the ratio of densities of 2 gases, O2 & N2, having partial pressures in the ratio 2:3?(a) 16/21(b) 12/7(c) 21/16(d) 7/12This question was addressed to me in a job interview.I need to ask this question from Kinetic Theory topic in section Kinetic Theory of Physics – Class 11
Answer» The correct answer is (a) 16/21 Easiest explanation: The RATIO of MOLES is the same as the ratio of PARTIAL pressures. The ratio of DENSITIES: d1/d2= (m1/V)/(m2/V) = m1/m2= (n1M1)/(n1M2), where n is the number of moles and M is the molecular mass.d1/d2= (2/3)*(16/14) = 16/21.

Discussion

4.	The behavior of real gases approaches that of ideal gas in which of these following conditions?(a) Low pressure & low temperature(b) High Pressure & high temperature(c) Low pressure & high temperature(d) high pressure & low temperatureThis question was addressed to me in an interview for internship.My enquiry is from Kinetic Theory topic in portion Kinetic Theory of Physics – Class 11
Answer» The correct choice is (c) LOW pressure & high TEMPERATURE The best I can explain: Ideal gas is based on the assumptions of kinetic THEORY of gases(KTG). At low pressure and high temperature the intermolecular forces become less significant and the size of molecules becomes less as COMPARED to separation between them. These are two postulates of KTG and hence in these conditions real gas behavior is SIMILAR to that of ideal gases.

Discussion

5.	Which of the following is not an assumption of KTG?(a) Time spent during collision is negligibly small(b) All gases are made up of molecules moving randomly in all directions(c) Molecules do not collide with each other(d) Molecules collide elastically with the wallThe question was asked during a job interview.My doubt is from Kinetic Theory of an Ideal Gas topic in chapter Kinetic Theory of Physics – Class 11
Answer» Right choice is (c) MOLECULES do not collide with each other Easiest explanation: According to KTG, molecules collide elastically with each other and with the walls of the container. The other GIVEN assumptions are true. These assumptions help to develop a model of molecular BEHAVIOR of an ideal GAS.

Discussion

6.	What is the ratio of specific heats for a diatomic gas?(a) 7/5(b) 5/3(c) 9/7(d) 7/2I had been asked this question in class test.This intriguing question comes from Kinetic Theory in division Kinetic Theory of Physics – Class 11
Answer» Right option is (a) 7/5 To explain I would SAY: The value of CV for a DIATOMIC GAS is 7/2 R and CP is 9/2 R. Thus the value of γ is: CP/CV = 7/5.

Discussion

7.	Consider a gas inside a box. It exerts some pressure on its walls. Find this value. GIven that number of molecules per unit volume be 20, mass of each molecule 10^-20kg, vx^2 = 1m^2/s^2.(a) 2010^-20Pa(b) 20/310^-20Pa(c) 20/310^-19Pa(d) 2010^-19PaI have been asked this question in examination.My question comes from Kinetic Theory of an Ideal Gas in portion Kinetic Theory of Physics – Class 11
Answer» RIGHT option is (a) 2010^-20Pa To explain I would SAY: Pressure is given by (1/3)nmv^2. v^2 = 3vx^2 = 3m^2/s^2. P = (1/3)2010^-203 = 20*10^-20Pa.

Discussion

8.	John Dalton said that atoms are the smallest constituents of elements. True or False?(a) True(b) FalseThis question was addressed to me in final exam.This interesting question is from Kinetic Theory in portion Kinetic Theory of Physics – Class 11
Answer» Correct choice is (a) True The best EXPLANATION: Dalton had proposed the atomic theory to explain the laws of definite and multiple proportions. He SAID that atoms are the SMALLEST constituents of ELEMENTS.

Discussion

9.	What is the number of molecules in 2.24L of SO2 at STP?(a) 6.02310^23(b) 6.02310^22(c) 6.02310^20(d) 6.02310^21This question was addressed to me by my college professor while I was bunking the class.Query is from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11
Answer» The correct answer is (B) 6.02310^22 Easiest explanation: ACCORDING to Avogadro’s LAW 22.4L of any GAS at STP is 6.02310^23. So, in 2.24L there will be 6.02310^23/10 = 6.02310^22.

Discussion

10.	Which of the following states of matter has the maximum value of mean free path?(a) Gas(b) Solid(c) Liquid(d) PlasmaThis question was addressed to me by my school teacher while I was bunking the class.Question is taken from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11
Answer» RIGHT answer is (a) Gas To elaborate: The atoms of gas have the most interatomic SPACE and can therefore TRAVEL freely. This is why they travel longer distances without colliding and are therefore said to have the MAXIMUM mean FREE path.

Discussion

11.	What is the number of molecules in 3 cubic metre of a gas at 3atm & 27°C?(a) 2.1710^-20(b) 6.3810^-20(c) 3.8610^-20(d) 4.5810^-20The question was posed to me in exam.My question comes from Kinetic Theory of an Ideal Gas in division Kinetic Theory of Physics – Class 11
Answer» The CORRECT choice is (a) 2.1710^-20 For explanation: USING, PV=NkT we get: N = PV/kT = (3310^5)/(1.3810^-23300) = 2.1710^-20.

Discussion

12.	There are 3 non-interacting ideal gases in a container. The moles of gases 1,2 & 3 are in the ratio 1:3:5. If the total pressure is 54Pa, find the value of partial pressure of gas 1.(a) 6Pa(b) 12Pa(c) 18Pa(d) 28PaI had been asked this question in an interview for job.The doubt is from Kinetic Theory topic in section Kinetic Theory of Physics – Class 11
Answer» The correct CHOICE is (a) 6Pa The best explanation: The ratio of PARTIAL pressures will be in the same ratio as that of moles, i.e: 1:3:5. Let the partial pressure of gas 1 be ‘x’. THUS, x+3x+5x = 54. x = 6Pa.

Discussion

13.	How many degrees of freedom are there in a monatomic gas?(a) 1(b) 2(c) 3(d) 0I have been asked this question in an online interview.This intriguing question originated from Kinetic Theory in division Kinetic Theory of Physics – Class 11
Answer» Right CHOICE is (c) 3 The BEST I can EXPLAIN: A monatomic GAS has 3 translational degrees of FREEDOM.

Discussion

14.	A container has 3 gases whose mass ratio is 1:3:5. What is the ratio of mean square speed of the molecules of two gases? Their atomic masses are 20u, 30u & 40u corresponding to the order in which the ratios are given.(a) 2:3:4(b) 4:3:2(c) 2:√3:√2(d) √2:√3:2I had been asked this question by my school principal while I was bunking the class.This is a very interesting question from Kinetic Theory of an Ideal Gas topic in chapter Kinetic Theory of Physics – Class 11
Answer» The correct OPTION is (b) 4:3:2 The BEST I can explain: Their average kinetic energies will be the same.Thus, 1/2mv^2will be the same. v1^2:v2^2:v3^2 =m3:m2:m1 = 40:30:20 = 4:3:2.

Discussion

15.	Consider a gas enclosed in a box. Let the walls have an area of 0.01m^2. Let’s say a few molecules having their x-component of velocity =2m/s, hit a wall parallel to the yz plane. What will be the value of force on the wall in time dt? Let the number of molecules per unit volume be 10 & mass of each molecule be 10^-20kg.(a) 410^-19N(b) 410^-21N(c) 4/310^-21N(d) 4/310^-19NThe question was asked by my school principal while I was bunking the class.Enquiry is from Kinetic Theory of an Ideal Gas topic in portion Kinetic Theory of Physics – Class 11
Answer» RIGHT option is (b) 410^-21N Best explanation: According to the assumptions of KTG, we will assume that the molecules COLLIDE elastically. The total momentum transferred to the wall is 2MV(1/2)nAvdt. 1/2 has been included because, on average, half the molecules NEAR that wall will be moving AWAY from the wall. Force will be momentum/time = nmAv^2 = 1010^-200.014 = 410^-21N.

Discussion

16.	Average kinetic energy of a gas depends on which of the following factors?(a) Nature of gas(b) Temperature(c) Pressure(d) VolumeI got this question during an interview.My question is taken from Kinetic Theory of an Ideal Gas in portion Kinetic Theory of Physics – Class 11
Answer» The correct option is (b) TEMPERATURE The BEST I can explain: AVERAGE kinetic ENERGY is given by (3/2)kBT, which shows that it only depends on temperature.

Discussion

17.	What is the mass of 22.4L of CO2at STP?(a) 1g(b) 44g(c) 44kg(d) 1kgI had been asked this question in an interview for job.This interesting question is from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11
Answer» CORRECT choice is (b) 44g To EXPLAIN: 22.4L of a GAS at STP has a WEIGHT equal to its molar mass. So, the weight of CO2 will be 12+16+16 = 44g.

Discussion

18.	The number of molecules per unit volume in the sample is 20. The mass of each molecule is 10^-20kg. The mean of speed squared is 4m^2/s^2. What is the value of internal energy of the gas? Assume volume of container is 0.02m^3.(a) 0.810^-20J(b) 0.5310^-20J(c) 0.0110^-20J(d) 0.4510^-20JThe question was posed to me during an interview for a job.This interesting question is from Kinetic Theory of an Ideal Gas in portion Kinetic Theory of Physics – Class 11
Answer» Correct ANSWER is (a) 0.810^-20J The explanation: INTERNAL ENERGY is given by: E = (1/2)Nmv^2, where N is the total NUMBER of molecules = nV. E = 0.5200.0210^-204 = 0.810^-20J.

Discussion

19.	What is meant by mean free path?(a) It is the average distance a molecule travels without colliding(b) Average distance between 2 molecules(c) Average distance travelled by a molecule before colliding with a wall of the container(d) Sum of distance travelled by all moleculesThis question was posed to me during an interview.My doubt stems from Kinetic Theory topic in section Kinetic Theory of Physics – Class 11
Answer» Right CHOICE is (a) It is the average distance a molecule travels WITHOUT COLLIDING To explain I would SAY: Mean free path of a molecule is defined as the average distance TRAVELLED by molecules before colliding.

Discussion

20.	Consider a gas enclosed in a box. A molecule of mass m, having a velocity -2i+3j+4k collides with a wall parallel to the xz plane. What will be its velocity after collision and its change in momentum? i,j & k are unit vectors along the x,y & z axis.(a) -2i-3j+4k, -6mj(b) 2i+3j-4k, -6mj(c) -2i-3j+4k, 6mj(d) 2i+3j-4k, 6mjThe question was asked in an online quiz.I would like to ask this question from Kinetic Theory of an Ideal Gas in division Kinetic Theory of Physics – Class 11
Answer» RIGHT answer is (a) -2i-3j+4k, -6MJ To elaborate: On COLLISION with a WALL parallel to the xz plane, only the y-component will change. Thus, new velocity will be -2i-3j+4k. The change in MOMENTUM will be -3mj-3mj = -6mj.

Discussion

21.	How many degrees of freedom are there in a diatomic gas?(a) 2(b) 5(c) 3(d) 1I have been asked this question in my homework.Enquiry is from Kinetic Theory in division Kinetic Theory of Physics – Class 11
Answer» Right choice is (b) 5 The best explanation: A DIATOMIC gas has 3 translational DEGREES of FREEDOM and 2 ROTATIONAL degrees of freedom. Thus, the total number of degrees of freedom is 5.

Discussion

Explore topic-wise InterviewSolutions in .

What is the ratio of specific heats for a monatomic gas?(a) 5/3(b) 5/2(c) 7/5(d) 9/5This question was posed to me in exam.My question is based upon Kinetic Theory in section Kinetic Theory of Physics – Class 11

Boyle’s law can be deduced from kinetic theory. True or False?(a) True(b) FalseThis question was addressed to me in class test.My question is from Kinetic Theory of an Ideal Gas topic in section Kinetic Theory of Physics – Class 11

What is the ratio of densities of 2 gases, O2 & N2, having partial pressures in the ratio 2:3?(a) 16/21(b) 12/7(c) 21/16(d) 7/12This question was addressed to me in a job interview.I need to ask this question from Kinetic Theory topic in section Kinetic Theory of Physics – Class 11

What is the ratio of specific heats for a diatomic gas?(a) 7/5(b) 5/3(c) 9/7(d) 7/2I had been asked this question in class test.This intriguing question comes from Kinetic Theory in division Kinetic Theory of Physics – Class 11

John Dalton said that atoms are the smallest constituents of elements. True or False?(a) True(b) FalseThis question was addressed to me in final exam.This interesting question is from Kinetic Theory in portion Kinetic Theory of Physics – Class 11

What is the number of molecules in 2.24L of SO2 at STP?(a) 6.023*10^23(b) 6.023*10^22(c) 6.023*10^20(d) 6.023*10^21This question was addressed to me by my college professor while I was bunking the class.Query is from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11

Which of the following states of matter has the maximum value of mean free path?(a) Gas(b) Solid(c) Liquid(d) PlasmaThis question was addressed to me by my school teacher while I was bunking the class.Question is taken from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11

What is the number of molecules in 3 cubic metre of a gas at 3atm & 27°C?(a) 2.17*10^-20(b) 6.38*10^-20(c) 3.86*10^-20(d) 4.58*10^-20The question was posed to me in exam.My question comes from Kinetic Theory of an Ideal Gas in division Kinetic Theory of Physics – Class 11

How many degrees of freedom are there in a monatomic gas?(a) 1(b) 2(c) 3(d) 0I have been asked this question in an online interview.This intriguing question originated from Kinetic Theory in division Kinetic Theory of Physics – Class 11

Average kinetic energy of a gas depends on which of the following factors?(a) Nature of gas(b) Temperature(c) Pressure(d) VolumeI got this question during an interview.My question is taken from Kinetic Theory of an Ideal Gas in portion Kinetic Theory of Physics – Class 11

What is the mass of 22.4L of CO2at STP?(a) 1g(b) 44g(c) 44kg(d) 1kgI had been asked this question in an interview for job.This interesting question is from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11

How many degrees of freedom are there in a diatomic gas?(a) 2(b) 5(c) 3(d) 1I have been asked this question in my homework.Enquiry is from Kinetic Theory in division Kinetic Theory of Physics – Class 11

What is the number of molecules in 2.24L of SO2 at STP?(a) 6.02310^23(b) 6.02310^22(c) 6.02310^20(d) 6.02310^21This question was addressed to me by my college professor while I was bunking the class.Query is from Kinetic Theory topic in chapter Kinetic Theory of Physics – Class 11

What is the number of molecules in 3 cubic metre of a gas at 3atm & 27°C?(a) 2.1710^-20(b) 6.3810^-20(c) 3.8610^-20(d) 4.5810^-20The question was posed to me in exam.My question comes from Kinetic Theory of an Ideal Gas in division Kinetic Theory of Physics – Class 11