CBSE Questions for Class 11 Engineering Physics Kinetic Theory Quiz 10 - MCQExams.com

Mean kinetic energy(or average energy) per gm molecule of a monoatomic gas is given by:
  • 3RT/2
  • kT/2
  • RT/2
  • 3kT/2
The de-Broglie wavelength of a particle accelerated with $$150\ volt$$ potential is $$10^{-10}\ m$$. If it accelerated by $$600\ volts$$ p.d. its wavelength will be
  • $$0.25\ A^{o}$$
  • $$0. 5\ A^{o}$$
  • $$1.5\ A^{o}$$
  • $$2\ A^{o}$$
We have a jar A filled with gas characterized by parameters P, V and T and another jar B filed with gas with parameters 2P, Vl4 and 2T, where the symbols have their usual meanings. The ratio of the number of molecules of jar A to those of jar B is 
  • 1 : 1
  • 1 : 2
  • 2 : 1
  • 4 : 1
If $$\triangle E$$ is the heat of reaction for $${ C }_{ 2 }{ H }_{ 3 }{ OH }_{ \left( 1 \right)  }+{ 3O }_{ 2\left( g \right)  }\rightarrow { 2CO }_{ 2\left( s \right)  }+3{ H }_{ 2 }{ 0 }_{ \left( 1 \right)  }$$ at constant volume, the $$\triangle H$$ ( Heat of reaction at constant pressure) at constant temperature is:
  • $$\triangle H=\triangle E+2RT$$
  • $$\triangle H=\triangle E-2RT$$
  • $$\triangle H=\triangle E+RT$$
  • $$\triangle H=\triangle E-RT$$
At what temperature does the average translational kinetic energy of a molecule in a gas become equal to kinetic energy of an electron accelerated from rest through a potential difference of $$1 \ volt$$?$$(k=1.38\times10^{23} \ J/k)$$
  • $$3770K$$
  • $$7370K$$
  • $$7730K$$
  • $$7330K$$
The total kinetic energy of $$1$$ mole of $$N_2$$ at $$27$$C will be approximately
  • 3739.662 J 
  • 1500 calorie
  • 1500 kilo calorie
  • 1500 erg.
Three perfect gasses at absolute temperatures $$T_1$$, $$T_2$$ and $$T_3$$ are mixed. If number of molecules of the gasses are $$n_1$$, $$n_2$$ and $$n_3$$ respectively then temperature of mixture will be (assume no loss of energy)
  • $$\dfrac{ T_{1}+ T_{2}+T_{3}}{3}$$
  • $$\dfrac{ { n }_{ 1 }^{ 2 } T_{1}+ { n }_{ 2 }^{ 2 } T_{2}+ { n }_{ 3 }^{ 2 } T_{3}}{{ n }_{ 1 }+{ n }_{ 2 }+{ n }_{ 3 }}$$
  • $$\dfrac{ { n }_{ 1 } T_{1}+ { n }_{ 2 }T_{2}+ { n }_{ 3 }T_{3}}{{ n }_{ 1 }+{ n }_{ 2 }+{ n }_{ 3 }}$$
  • $$\dfrac{ T_{1}+ T_{2}+T_{3}}{{ n }_{ 1 }+{ n }_{ 2 }+{ n }_{ 3 }}$$
Calculate $$\gamma $$ (ratio of $$C_p$$ and $$C_v$$ ) for triatomic linear gas at high temperature. Assume that the contribution of the vibrational degree of freedom is 75%?
  • 1.222
  • 1.121
  • 1.18
  • 1.33
A vessel has $$6g$$ of oxegen at pressure $$P$$ and temperature $$400\ K$$. A small hole is made in it so that oxygen leaks out. How much oxygen leaks out if the final pressure is $$P/2$$ and temperature is $$300\ K$$
  • $$3g$$
  • $$2g$$
  • $$4g$$
  • $$5g$$
A gas undergoes a process such that $$P \propto \dfrac{1}{T}$$. If the molar heat capacity for this process is $$24.93 \,J/mol \,K$$, then what is the degree of freedom of the molecules of the gas?
  • $$8$$
  • $$4$$
  • $$2$$
  • $$6$$
The degrees of freedom of a triatomic gas is? (consider moderate temperature)
  • $$6$$
  • $$4$$
  • $$2$$
  • $$8$$
Change in momentum of the gas molecules as they strike the walls
One mole of an ideal gas (mono-atomic) at temperature $$T_{0}$$ expands slowly according to law $$P^{2} = cT$$ ($$c$$ is constant). If final temperature is $$2T_{0}$$, heat supplied to gas is
  • $$2RT_{0}$$
  • $$\dfrac {3}{2}RT_{0}$$
  • $$RT_{0}$$
  • $$\dfrac {RT_{0}}{2}$$
Which graph shows how the average kinetic energy of the particles varies with absolute temperature for an ideal gas?
The effect of temperature on Maxwell's speed distribution is correctly shown by 
Select the incorrect relation. (Where symbols have their usual meanings)
  • $${ C }_{ p }=\dfrac { \gamma R }{ \gamma -1 }$$
  • $${ C }_{ p }-{ C }_{ v }=R$$
  • $$\Delta U=\dfrac { { P }_{ f }{ V }_{ f }-{ P }_{ i }{ V }_{ i } }{ 1-\gamma }$$
  • $${ C }_{ v }=\dfrac { R }{ \gamma -1 }$$
The ratio of adiabatic to isothermal elasticity of  diatomic gas is:-
  • $$1.67$$
  • $$1.4$$
  • $$1.33$$
  • $$1.27$$
A vessel contains 28 gm of $$N-2$$ and 32 gm of $$O_2$$ at temperature T = 1800 K and pressure 2 atm pressure it $$N_2$$ dissociates $$30%$$ and $$O_2$$ dissociates $$50%$$ if temperature remains constant. 
  • 2 atm
  • 1 atm
  • 2.8 atm
  • 1.4 atm
An ideal gas has an initial volume $$V$$ and pressure $$P$$. In doubling its volume the minimum work done will be in (of the given processes):
  • Isobaric process
  • Isothermal process
  • Adiabatic process
  • Same in all given processes
The velocities of sound in an ideal gas at temperature $$T_1$$ and $$T_2 k$$ are found to be $$V_1$$ and $$V_2$$ respectively.If the r.m.s. velocities of the molecules of the same gas at the same temperatures $$T_1$$ and $$T_2$$ are $$v_1$$ and $$v_2$$ respectively then
  • $$v_2=v_1(\dfrac{V_1}{V_2})$$
  • $$v_2=v_1(\dfrac{V_2}{V_1})$$
  • $$v_2=v_1\sqrt{\dfrac{V_2}{V_1}}$$
  • $$v_2=v_1\sqrt{\dfrac{V_1}{V_2}}$$
For gas, if the ratio of specific heats at constants pressure $$P$$ and constant volume $$V$$ is $$\gamma $$, then the value of degree of freedom is:
  • $$\dfrac{\gamma +1}{\gamma -1}$$
  • $$\dfrac{\gamma -1}{\gamma +1}$$
  • $$\dfrac{1}{2}(\gamma-1)$$
  • $$\dfrac{2}{\gamma-1}$$
A vessel contains a non-linear triatomic gas. If $$50$$% of gas dissociate into individual atom, then find new value of degree of freedom by ignoring the vibrational mode and any further dissociation 
  • $$2.15$$
  • $$3.75$$
  • $$5.25$$
  • $$6.35$$
At which of the following temperature would the molecules of a gas have twice the average kinetic energy they have at $${20}^{o}C$$
  • $${40}^{o}C$$
  • $${80}^{o}C$$
  • $${313}^{o}C$$
  • $${586}^{o}C$$
The lowest pressure(the best Vaccum) that can be created in laboratory at 27 degree is $$10^{-11} $$ mm of Hg. At this pressure, the number of ideal gass molecules per $$cm^{3}$$ will be
  • $$3.22 \times 10 ^{12} $$
  • $$1.61 \times 10 ^{12} $$
  • $$3.21 \times 10 ^{6} $$
  • $$3.22 \times 10 ^{5} $$
The internal energy of an ideal gas increases during an isothermal process when the gas is 
  • Expanded by adding more molecules to it
  • Expanded by adding more heat to it
  • Expanded against zero pressure
  • Compressed by doing work on it
One-gram mole of nitrogen occupies $$ 2 \times 10^4 $$ cc at a pressure of $$ 10^6  dynes/cm^2 $$. The average energy of a nitrogen molecule (in erg) will be:$$ (Avogadro's number = 6 \times 10^25 ) $$
  • $$ 14 \times 10^{-13} $$
  • $$ 10 \times 10^{12}  $$
  • $$ 10^6 $$
  • $$ 2 \times 10^6 $$
The molecules of a given mass of gas have rms velocity $$200\ ms^{-1}$$ at $$27^{\circ}C$$ and $$10^5\ Nm^{-2}$$ pressure. When the absolute temperature is doubled and the pressure is halved, the rms speed of the molecules of the same gas is:
  • $$200\ ms^{-1}$$
  • $$400\ ms^{-1}$$
  • $$200\sqrt{2}\ ms^{-1}$$
  • $$400\sqrt{2}\ ms^{-1}$$
In a thermodynamic system, working substance is ideal gas, its internal energy is in the form of  
  •  kinetic energy
  •  kinetic and potential energy
  •  potential energy
  •  None of the above
$$T_1$$ is the temperature of oxygen enclosed in a cylinder. The temperature is increased to $$T_2$$ and Maxwellan distribution curves for $$O_2$$ at temperature $$T_1$$ and $$T_2$$ are plotted. If $$A_1$$ and $$A_2$$ are the areas under the curves and the speed axis, in both cases , then 
  • $$A_1 > A_2$$
  • $$A_1 < A_2$$
  • A_1 = A_2$$
  • $$A_1=\sqrt {A_2}$$
Molar heat capacity of water in equilibrium with ice at constant pressure is 
  • Zero
  • $$\infty $$
  • 40.45 kJ $$K^{-1}mol^{-1}$$
  • 75.48 $$JK^{-1}mol^{-1}$$
The speed of a longitudinal wave in a mixture containing 4 moles of He and 1 mole of Ne at 300 K will be
  • 930 m/s
  • 541 m/s
  • 498 m/s
  • None of these
In a process the pressure of gas is inversely proportional to the square of volume If temperature of the gas is increased then work done by the gas
  • Is positive
  • Is negative
  • Is zero
  • May be positive
Hydrogen is a diatomic gas. Its molar specific heat at constant volume is very nearly
  • $$\frac { 3 R } { 2 }$$
  • $$\frac { 5 R } { 2 }$$
  • $$\frac { 7 R } { 2 }$$
  • (b) or (c) depending on the temperature.
In a thermodynamic system, working substance is ideal gas, its internal energy is in the form of
  • Kinetic energy
  • Kinetic and potential energy
  • Potential energy
  • None of the above
In a diatomic molecule, the rotational energy at a given temperature
  • obeys Maxwell's distribution.
  • have the same value for all molecules.
  • equals the translational kinetic energy for each molecule.
  • is (2/3) rd the translational kinetic energy for each molecule.
 The total kinetic energy of $$8$$ litres of helium molecules at $$5$$ atmosphere pressure will be
($$1$$ atmosphere = $${ 1.013\times 10 }^{ 5 }$$pascal)
  • $$\text{607 J}$$
  • $$\text{6078 J}$$
  • $$\text{607 erg}$$
  • $$\text{6078 erg}$$
$$2$$ grams of mono atomic gas occupies a volume of $$2$$ litres at a pressure of $$8.3 \times 10^5$$ Pa and $$127^0C$$. Find the molecular weight of the gas.
  • $$2$$ grams/mole
  • $$16$$ grams/mole
  • $$4$$ grams/mole
  • $$32$$ grams/mole
Two moles of an ideal gas X occupying a volume V excert a pressure P. The same pressure is excert by one mole of another gas Y occupying a volume 2V. (if the molecular weight of Y is 16 times the molecular weight of X), find the ratio of the 'rms' speed of the molecular of X and Y.
  • $$2$$
  • $$4$$
  • $$\frac { 1 }{ 2 } $$
  • $$\sqrt { 2 } $$
The temperature of a diatomic gas is T. The total kinetic energy of the gas is given as $$E = { K }_{ 1 }$$ where $${ K }_{ 1 }$$ is constant. Find out the total number of molecules of the gas in the sample. (K = Boltzaman's constant)
  • $$3K_{ 1 }K$$
  • $$5K_{ 1 }/2K$$
  • $$2K_{ 1 }/5K$$
  • None of these
let A and B the two gases and given :
$$\frac{{T}_{A}}{{M}_{A}}$$ =$$\frac{{T}_{B}}{{M}_{B}}$$  Where T is the temperature and M is molecular mass. If $${C}_{A}$$ and  $${C}_{B}$$ are the r.m.s. speed, then the ratio $$\frac{{C}_{A}}{{C}_{B}}$$ will be equal to:
  • 2
  • 4
  • 1
  • 0.5
If hydrogen gas is heated to a very high temperature, then the fraction of energy possessed by gas molecules correspond to rotational motion:-
  • $$\dfrac{3}{5}$$
  • $$\dfrac{2}{7}$$
  • $$\dfrac{3}{7}$$
  • $$\dfrac{2}{5}$$
A gas is filled in a cylinder. Its temperature is increased by $$20\%$$ and volume decreases by $$20\%$$. If pressure remains constant, what percentage of mass of the gas leaks out?
  • $$33.33\%$$
  • $$66.67\%$$
  • $$20\%$$
  • $$40\%$$
The rms speed of $${ N }_{ 2 }$$ molecular at STP (P=1 tm; T=$${ 0 }^{ 0 }C$$) is.....
(the density of $${ N }_{ 2 }$$ in these conditions is 1.25 $${ kg/m }^{ 3 }$$
  • 493 m/s
  • 390 m/s
  • 290 m/s
  • 590 m/s
An ant is moving on a plane horizontal surface. The number of degrees of freedom of the ant will be
  • 1
  • 2
  • 3
  • 6
When $$2 gm$$ of gas is introduced into an evacuated flask kept at $$25^oC$$ the pressure is found to be one atmosphere. If $$3 gm$$ of another gas added to the same flask the pressure becomes $$1.5$$ atmospheres. The ratio of the molecular weights of there gases will be
  • $$1:3$$
  • $$3:1$$
  • $$1:2$$
  • $$3:2$$
If $$\gamma $$ be the ration of specific heats of a perfect gas, the number of degree of freedom of a molecule of the gas is:
  • $$\dfrac{{25}}{2}\left( {\gamma - 1} \right)$$
  • $$\dfrac{{3\gamma - 1}}{{2\gamma - 1}}$$
  • $$\dfrac{2}{{\gamma - 1}}$$
  • $$\dfrac{9}{2}(\gamma - 1)$$
The degree of freedom of a diatomic gas at normal temperature is.
  • $$7$$
  • $$6$$
  • $$5$$
  • $$4$$
A real gas most closely approaches the behaviour of an ideal gas at :
  • 15 atm and 200 K
  • 1 atm and 273 K
  • 0.5 atm and 500 K
  • 15 atm and 500 K
When an ideal monoatomic  gas is heated zt constant pressure , which of the following may be true
  • $$\dfrac {dU}{dQ} = \frac {3}{5}$$
  • $$\dfrac {dW}{dQ} = \frac {2]}{5}$$
  • $$\dfrac {dU}{dQ} = \frac {4}{5}$$
  • $$dW + dU = dQ $$
A gas mixture contains 8 moles of oxygen and 2 mole of argon at room temperature T. The total energy of the mixture is 
  • 11 RT
  • 23 RT
  • 22 RT
  • 26 RT
The kinetic energy for 14 grams of nitrogen gas at  $$127$$  is nearly (mol. mass of nitrogen  $$= 28$$  and gas constant  $$=8.31{ JK }_{ -1 }{ mol }_{ -1 }$$ )
  • $$1.0J$$
  • $$4.15J$$
  • $$2493J$$
  • $$3.3J$$
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