Physics

Thermodynamics and Gas Laws

626 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 chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

"All gases have the same number of moles in the same volume at constant temperature and pressure:. This statments belongs to :

  1. Boyle's law

  2. Charles's law

  3. Avogadro's principle

  4. ideal gas law

  5. Dalton's law
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Avogadro's law (sometimes referred to as Avogadro's hypothesis or Avogadro's principle) is an experimental gas law relating volume of a gas to the amount of substance of gas present.
Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules".
For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Avogadro's law shows the relationship between which two variables?

  1. Volume and number of moles

  2. Pressure and number of moles

  3. Volume and pressure

  4. Temperature and pressure

  5. Temperature and number of moles
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

(A) : Volume and number of moles, : at constant pressure.
Avogadro Law: At the same condition of temperature and pressure the volume of the gas is directly proportional to the number of the moles.

Multiple choice physics floating bodies pressure exerted by a liquid column pressure at a certain depth in liquid variation of pressure with depth

A column of mercure of lenath $h = 10 \mathrm { cm }$ is contained in the middle of a narrow horizontal tube of length $1 \mathrm { m } ,$ closed at both ends. The air in both halves of the tube is under a pressure of $P _ { 0 } = 76 \mathrm { cm }$ of mercury. The tube is now slowly made vertical. The distance moved by mercury will be approximately

  1. $4.5$ $\mathrm { cm }$
  2. $3.0$ $\mathrm { cm }$
  3. $2.5$ $\mathrm { cm }$
  4. $1.2$$ $\mathrm { cm }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When the tube is vertical, the pressure in the trapped air changes according to Boyle's law (P1V1 = P2V2). The mercury column shifts to balance the pressure difference between the top and bottom air columns. Calculation based on the pressure change leads to a shift of approximately 3 cm.

Multiple choice physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

A certain quantity of heat energy is given to a diatomic ideal gas which expands at constant pressure. The fraction of the heat energy that is converted into work is 

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

Supplied heat at constant pressure, 

$\Delta Q=nC _P \Delta T$
Change in internal energy,
$\Delta U=nC _V \Delta T$
ratio, $\dfrac{\Delta U}{\Delta Q}=\dfrac{nC _V \Delta T}{nC _P \Delta T}=\dfrac{C _V}{C _P}$. . . . . . . . .(1)
For diatomic ideal gas,
$C _P=\dfrac{7R}{2}\,  ,  C _V=\dfrac{5R}{2}$
From equation (1), we get
$\dfrac{\Delta U}{\Delta Q}=\dfrac{5R/2}{7R/2}=\dfrac{5}{7}$
$(5/7)^{th}$ part of heat supplied is used to increase internal energy.

Multiple choice physics the essence of change different forms of energy energy conversions energy transformations and energy transfers

An ideal gas heat engine operates in a Carnot's cycle between $227^{\circ}C$ and $127^{\circ}C$. It absorbs $6\times 10^{4} J$ at high temperature. The amount of heat converted into work is _____.

  1. $4.8\times 10^{4}J$
  2. $3.5\times 10^{4}J$
  3. $1.6\times 10^{4}J$
  4. $1.2\times 10^{4}J$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Efficiency of Carnot engine = 1 - (T_low / T_high) = 1 - (400 / 500) = 0.2. Work done = Efficiency * Heat absorbed = 0.2 * 6 * 10^4 = 1.2 * 10^4 J.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

At a temperature T K,the pressure of 4.0 g argon in a bulb is p.The bulb is put in a bath having temperature higher by 50 K than the one.0.8 g of argon gas had to be removed to maintained ariginal pressure.The temperature T is equal to 

  1. 510 K

  2. 200 K

  3. 100 K

  4. 73 K
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using PV = nRT. Initially: pV = (4/M)RT. Finally: pV = (3.2/M)R(T+50). Equating: 4T = 3.2(T+50) => 4T = 3.2T + 160 => 0.8T = 160 => T = 200 K.

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Give reasons as to why equal masses of different substances have different volumes.

  1. because they have different shapes

  2. because they have different densities

  3. because they have the same densities

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The mass of the substance is dependent on the density and volume of the substance. The substance having the same volume might have different mass because they have different densities.


Option $B$ is correct. 

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

An ideal gas is allowed to expand both reversibly and irreversibly in an isolated system. If $T _i$ is the initial temperature and $T _f$ is the final temperature , which of the following is correct?

  1. $T _f>T _i$ for reversible process but $T _f=T _i$ for irreversible process
  2. $(T _f)rev=(T _f)irrev$
  3. $T _f=T _i$ for both reversible and irreversible process
  4. $(T _i)irrev>(T _f)rev$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\triangle Q=\triangle U+ \triangle W$


Isolated system- adiabatic $\Rightarrow \triangle Q=0$


$0=\triangle U+ \triangle W$

$\Rightarrow \triangle W=- \triangle U$

For expansion, $\triangle W$ is positive and $\triangle U$ is negative.
This means $T _f<T _i$

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics
Under which of the following conditions is the relation,
$\triangle H=\triangle U+P\triangle V$ valid for a closed system?

  1. Constant pressure

  2. Constant temperature

  3. Constant temperature and pressure

  4. Constant temperature, pressure and composition
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\Delta H=\Delta U+\Delta(PV)$

$\implies \Delta H=\Delta U+P\Delta V+V\Delta P$
In constant pressure/ Isobasic process
$\implies \Delta H=\Delta U+P\Delta V$

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

In which case mean free path is not affected? 

  1. ${ H } _{ 2 }$ gas at$ { 100 }^{ 0 }C$ and $1 \ atm $ is transferred into a vessel at $ { 50 }^{ 0 }C$ and $0.5 \ atm$
  2. ${ O } _{ 2 }$ gas at $200 K$ and $2 \ atm$ is transferred into a vessel at $400 K$ and $1\ atm $
  3. ${ O } _{ 2 }$ gas is replaced by ${ H } _{ 2 }$ gas keeping other variables constant

  4. Medium is made more viscous
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
${ H } _{ 2 }$ gas at ${ 100 }^{ 0 }C$ and $1atm$ is transferred into a vessel at ${ 50 }^{ 0 }C$ and $0.5atm$.
in this case $\dfrac { P }{ T } =$ constant.
In this case mean free path not affected.
Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which statement BEST describes why work is a path function

  1. You finish at a different place

  2. You start at a different place

  3. The amount of work varies depending on which path you take to get to the destination

  4. The amount of work is the same whichever path you take to get to the destination

  5. Work is not a path function, it is a state function
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The statement (C) BEST describes why work is a path function.
The amount of work varies depending on which path you take to get to the destination.
State function is independent of the pah followed whereas path function is dependent on path followed.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Which of the following is path function?

  1. Work

  2. Specific volume

  3. Pressure

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

In thermodynamics, a state function or function of state is a function defined for a system relating several state variables or state quantities that depends only on the current equilibrium state of the system. State functions do not depend on the path by which the system arrived at its present state. A state function describes the equilibrium state of a system.

Hence, work is a path function and not state function.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

Work is __________ function.

  1. path

  2. state

  3. both path and state

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Work is a path function and not a state function. The amount of work done is different for different paths although the initial and final states are the same. The amount of work depends on the path connecting the initial and final states.

Multiple choice chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

An open vessel at $27^{\circ}C$ is heated until ($\tfrac 25$)th of the air in it has been expelled. Assuming that the volume of the vessel remains constant. Which of the following option is correct?

  1. Final temperature is 500 K

  2. Final volume is 2 times the initial volume

  3. Final pressure is 1 atm

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$T _{1}=27°C=27+273=300 K$


Let $n _{1}$ be n.

$n _{2}=n-\cfrac{2n}{5}=\cfrac{3n}{5}$

$T _{2}$=?

We know that, $n _{1}T _{1}=n _{2}T _{2}$

$\Longrightarrow n\times 300=\cfrac { 3n }{ 5 } \times { T } _{ 2 } \ \Longrightarrow { T } _{ 2 }=500K=500-273=227°C$