Physics

Thermodynamics and Gas Laws

616 Questions

Thermodynamics and gas laws questions test the understanding of ideal gas behavior, work done during thermodynamic processes, and specific heat ratios. Key areas include isothermal, adiabatic, and isobaric expansions along with real gas deviations. These mathematical physics concepts are standard in engineering and general science competitive exams.

Ideal gas equationIsothermal and adiabatic processesThermodynamic workGas kinetic theoryReal gas behavior

Thermodynamics and Gas Laws Questions

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

For a certain gas the heat capacity at constant pressure is greater than that at constant volume by $29.1 J/K$. How many moles of the gas are there?

  1. $13.5 \ mol $
  2. $9.5 \ mol $
  3. $7.5 \ mol $
  4. $3.5 \ mol $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

We know that for one mole of gas,


${ C } _{ P }-{ C } _{ V }=8.32J/K$

Hence, for n moles,

$n({ C } _{ P }-{ C } _{ V })=8.32n=29.1$

$n=3.5 mol$

Answer is $3.5 mol$

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

4.0 g of a gas occupies 22.4 litres at NTP. The specific heat capacity of the gas at constant volume is 5.0 ${ JK }^{ -1 }{ mol }^{ -1 }$. If the speed of sound in this gas at NTP is 952${ ms }^{ -1 }$, then the heat capacity at constant pressure is (Take gas constant R=8.3${ JK }^{ -1 }{ mol }^{ -1 }$)

  1. $8.5{ JK }^{ -1 }{ mol }^{ -1 }$
  2. $8.0{ JK }^{ -1 }{ mol }^{ -1 }$
  3. $7.5{ JK }^{ -1 }{ mol }^{ -1 }$
  4. $7.0{ JK }^{ -1 }{ mol }^{ -1 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

When an ideal diatomic gas is heated at a constant pressure, the fraction of the heat energy supplied which increases the internal energy of the gas is

  1. $\dfrac {2}{5}$
  2. $\dfrac {3}{5}$
  3. $\dfrac {3}{7}$
  4. $\dfrac {5}{7}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Th\quad fraction\quad is\quad \frac { \triangle V }{ \triangle Q } \quad =\quad \frac { { _{ n }{ C } _{ v } }\triangle T }{ { _{ n }{ C } _{ p } }\triangle T } \ \frac { \triangle V }{ \triangle Q } =\frac { { C } _{ V } }{ { C } _{ P } } \quad =\quad \frac { 1 }{ Y } \ as\quad we\quad know\quad y\quad =\quad { C } _{ P }/{ C } _{ V }\ y\quad for\quad diatomatic\quad gas\quad :\quad \ { C } _{ P }\quad of\quad diatometic\quad gas\quad :\quad \frac { 7 }{ 2 } \ { C } _{ V }\quad of\quad diatometic\quad gas\quad :\quad \frac { 5 }{ 2 } \ y\quad =\quad \frac { { C } _{ P } }{ { C } _{ V } } =\frac { 7/2 }{ 5/2 } =\frac { 7 }{ 5 } \ \frac { \triangle V }{ \triangle Q } =\frac { 1 }{ y } =\frac { 1 }{ 7/5 } =\frac { 5 }{ 7 } \quad (D)$

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

For an ideal gas, the heat capacity at constant pressure is larger than that at constant volume because

  1. positive work is done during expansion of the gas by the external pressure

  2. positive work is done during expansion by the gas against external pressure

  3. positive work is done during expansion by the gas against intermolecular forces of attraction

  4. more collisions occur per unit time when volume is kept constant
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When  heat  is  supplied  at  constant  volume,  temperature  increases accordingly  to  the  ideal  gas  equation.

$P=\dfrac { nRT }{ V } $

as  V  is  constant  and  T  is  increasing,  pressure  will  also  increase.

Than at constant pressure  as temperature is increase volume increases, resulting in expansion of the gas, resulting in positive work, Hence the heat given is used up for expansion and then to increases the internal energy . The heat capacity at constant pressure is larger.

Multiple choice physics wave motion wave velocity speed and acceleration of travelling wave speed of a travelling wave

If 'v' is the velocity of sound in a gas then 'v' is directly proportional to (where M, d and T represents molecular weight of gas, density of gas and its temperature respectively.)

  1. $\sqrt{M}$
  2. $\displaystyle \frac{1}{\sqrt{d}}$
  3. $\sqrt{T}$

  4. Both (2) and (3)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The speed of sound in a gas is given by v = sqrt(gamma * P / d) or v = sqrt(gamma * R * T / M). Since P/d = RT/M, v is proportional to sqrt(T) and inversely proportional to sqrt(M) or sqrt(d). Thus, both options 2 and 3 are correct.

Multiple choice

The amount of mass in a given volume is

  1. Pressure

  2. Volume

  3. Mass

  4. Density
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Density is a fundamental physical property defined as mass per unit volume. It measures how tightly packed the matter in an object or substance is.

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

Compressibility is minimum in case of :

  1. solid.

  2. liquid.

  3. both (a) and (b).

  4. gas.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In case of solid the inter-molecular force of attraction is very strong and inter-particle spaces are very small. So, it is very difficult to compress the solid.


Hence, the correct option is $A$.

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

Which of these is a property of a gas.

  1. Has a fixed volume

  2. Has a fixed shape

  3. Doesn't have a fixed volume

  4. Doesn't have a fixed shape
Reveal answer Fill a bubble to check yourself
C,D Correct answer
Explanation

The intermolecular forces in the case of gas are very very weak and hence the gas molecules are not at all held tightly. Thus a gas doesn't have a fixed shape at all.
Gases do not have a fixed volume too. It has the volume of the container in which it is kept.


Hence, the correct options are $C$ and $D$

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

The translational kinetic energy of $10^{20}$ molecules of nitrogen at a certain temperature is $0.63$ J. The temperature is:

  1. $23^o$ C
  2. $31.3^o$ C
  3. $30.1^o$ C
  4. $43.3^o$ C
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$K.E=\dfrac{3}{2}N K _BT$


$N=10^{20}, K _B=1.38\times 10^{-23}$ Joule/, KE$=0.63$ J

$0.63=\dfrac{3}{2}\times 10\times 1.38\times 10^{-23}\times T$

$\Rightarrow T=\dfrac{0.63\times 2}{1.383}\times 10^3$

     $T=304.3$K

     $T=31.3^o$ C.

Hence, option $B$ is correct.

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

At what temperature will the total translational kinetic energy of $0.30$ mole of He gas be the same as the total translational kinetic energy of $0.40$ mol of Ar at $400$ K?

  1. $533$ K
  2. $400$ K
  3. $300$ K
  4. $266$ K
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$n _1=0.30$ mol, $T _1=?$


$n _2=0.40$ mol, $T _2=400$ K

Using $n _1T _1=n _2T _2$

$0.3\times T _1=0.4\times T _2$

$T _1=\dfrac{4}{3}\times 400$

$=533$ K

Hence, option $A$ is correct.

Multiple choice chemistry matter in our surroundings diffusion in different states of matter properties of solids, liquid, and gas particle theory of matter

In which of the following conditions, the distance between the molecules of hydrogen gas would increase?

  1. increasing pressure on hydrogen contained in a closed container

  2. some hydrogen gas leaking out of the container

  3. increasing the volume of the container of hydrogen gas

  4. adding more hydrogen gas to the container without increasing the volume of the container
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

When hydrogen gas leaks out of the container, the molecules of the gas remaining in the container have more free space. Hence, distance between the gas molecules increases. By increasing the volume of the container also increases the distance between the molecules.