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 physics option b: engineering physics buoyancy floatation fluid pressure

A gas cylinder containing cooking gas can withstand a pressure of  $14.9 atm. $ The pressure gauge of cylinder indicates  $12 atm $ at  $27 ^ { \circ } \mathrm { C } . $  Due to sudden fire in building the temperature starts rising. The temperature at which the cylinder explodes is

  1. $42.5 ^ { \circ } C$
  2. $67.8 ^ { \circ } C$
  3. $99.5 ^ { \circ } C$
  4. $25.7 ^ { \circ } C$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Use Gay-Lussac's law: P₁/T₁ = P₂/T₂. Convert to Kelvin: 27°C = 300K. (12+1)atm /300K = 14.9atm/T₂, so T₂ = (14.9×300)/13 ≈ 343.8K = 70.8°C. Wait: pressure gauge reads 12, so absolute pressure is 13 atm. T₂ = (14.9×300)/13 ≈ 343.8K = 70.8°C. This doesn't match 99.5°C. Let me recalculate: For 99.5°C = 372.5K to be correct, we'd need P₁ to be different. Actually, if gauge reads relative to atmospheric, then absolute P₁ = 13 atm. At explosion P₂ = 14.9 atm. T₂ = (14.9/13)×300K = 343.8K = 70.8°C. Answer should be B, not C. However, the claimed answer is C (99.5°C). There might be different interpretation. If initial absolute P = 12 atm (not 13), then T₂ = (14.9/12)×300K = 372.5K = 99.5°C. This suggests gauge already shows absolute pressure, which is unusual. Given the answer key claims C, the question likely treats 12 atm as absolute pressure.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

Equal amount of same gas in two similar cylinders $A \text { and } B$,compressed to same final volume from same initial volume one adiabatically and another isothermally, respectively then  

  1. final pressure in $A$ is more than in $B$
  2. final pressure in $B$ is greater than in $A$

  3. final pressure in both able equal
  4. for the gas, value of $\gamma = \frac { C _ { p } } { C _ { V } }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Adiabatic compression (PV^gamma = constant) results in a higher final pressure than isothermal compression (PV = constant) for the same volume change, because gamma > 1.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

The pressure and temperature of two different gases is $P$ and $T$ having the volume $V$ for each. They are mixed keeping the same volume and temperature, the pressure of the mixture will be

  1. $P/2$
  2. $P$
  3. $2P$
  4. $4P$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If two gases at same P, V, T are mixed into the same volume V, the total pressure is the sum of partial pressures. Since n = PV/RT, total moles = n1 + n2 = 2PV/RT. New pressure = (2PV/RT) * RT/V = 2P.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

When the volume of gas is reduced at constant temperature, the pressure exerted by the gas on the walls of the container increases because

  1. each molecules hits the walls with greater speed

  2. each molecule loses more energy when it strikes the wall

  3. each molecule loses momentum when it strikes the wall

  4. the number of molecules striking the wall per unit time increase.
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

A container with insulating walls is divided into equal parts by a partition fitted with a value.One part is filled with an ideal gas at a pressure P and temperature T, whereas the other part is completely evacuted.If the value is suddenly opened,the pressure and temperature of the gas will be

  1. $ \dfrac {p}{2}, T $
  2. $ \dfrac {p}{2} , \frac {T}{2} $

  3. p,T
  4. $ p, \dfrac {T}{2}, $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is a free expansion of an ideal gas into a vacuum. Since the walls are insulating (adiabatic) and no work is done (expansion into vacuum), the internal energy remains constant, meaning the temperature T remains constant. The volume doubles, so the pressure halves.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Pressure depends on distance as, $P=\dfrac{\alpha}{\beta}exp\left(-\dfrac{\alpha z}{k\theta}\right)$, where $\alpha, \beta$ are constants, z is distance, k is Boltzmann's constant and $\theta$ is temperature. The dimension of $\beta$ are.

  1. $M^0L^0T^0$
  2. $M^{-1}L^{-1}T^{-1}$
  3. $M^0L^2T^0$
  4. $M^{-1}L^1T^2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Given, 

$P=\dfrac{\alpha}{\beta}e^{\dfrac{-\alpha z}{k\theta}}$

Since, the exponentials are devoid of dimensions, the exponential part of the equation is ignored.  

Rest we have, $P=\dfrac{\alpha}{\beta}$

Since, $\dfrac{\alpha z}{k\theta}=Dimensionless$

$\alpha=\dfrac{k\theta}{z}$

Kinetic energy $=\dfrac 32 kT$

$k=\dfrac{K.E}{T}$

$\implies [k]=[M^1L^2T^{-2}][K^{-1}]$

$\implies [z]=[L^{-1}]$

$\implies [\theta]=[K^{-1}]$

From these, we get the values of $\alpha$ as,

$[\alpha]=[M^1L^1T^{-2}]$

Now, we know the dimension of prressure, 

$[P]=M^1l^{-1}t^{-2}]$

$\beta=\dfrac{\alpha}{P}$

$\implies \beta=\dfrac{[M^1L^1T^{-2}]}{[M^1L^{-1}T^{-2}]}$

$\implies \beta=[M^0L^2T^0]$
Multiple choice physics energy management solar power plant production of electricity from solar energy solar equipment solar energy and its applications

Which of the following is/are macroscopic variables:

  1. Volume

  2. Temperature

  3. Pressure

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Macroscopic variable is a measurable quantity used to describe the complete state of the system. The state of a macroscopic system in equilibrium can be described in terms of measurable properties as temperature, pressure, and volume, which are also known as thermodynamic variables.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

The Vander waal's equation for gas is given by $\left (P + \dfrac {a}{V^{2}}\right )(V - b) = RT$ where $P$ is pressure, $V$ is volume $'a'$ and $'b'$ are constants, $R$ is universal gas constant and $T$ is absolute temperature. Then the units of $'a'$ are

  1. $dyne\times cm^{5}$
  2. $dyne\times cm^{4}$
  3. $dyne\times cm^{3}$
  4. $dyne\times cm^{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the equation (P + a/V^2)(V - b) = RT, the term a/V^2 must have the same units as pressure P. Thus, units of a = units of P * units of V^2. Pressure is force/area (dyne/cm^2 in CGS) and volume is length^3 (cm^3). So, a = (dyne/cm^2) * (cm^3)^2 = dyne * cm^4.

Multiple choice zoology gas exchange and smoking gas exchange gas exchange in humans respiratory system in humans

According to Boyle's law, the product of pressure and volume is constant, hence.

  1. If volume of lung is increased, the pressure decreases proportionately

  2. If volume of lung is increased, the pressure also increases proportionately

  3. If volume of lungs is increased, the pressure decreases disproportionately

  4. If volume of lungs is increased, the pressure remains the same
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Boyle's Law states that pressure is inversely proportional to volume (P = k/V). Thus, increasing the volume of the thoracic cavity decreases the pressure inside the lungs.

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.

  1. Boyle's Law

  2. Charles's Law

  3. Avogadro's Principle

  4. Ideal Gas Law
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to the Avogadro's principal, every gas have the same number of moles in the same volume at constant temperature and pressure.

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 T and P is stated by :

  1. Boyle's law

  2. Charle's law

  3. Avogardro's law

  4. ideal gas law

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

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

According to Avogadro's hypothesis, equal volumes of gases under the same conditions of temperature and pressure will contain:

  1. the same number of molecules

  2. different number of molecules

  3. the same number of molecules only if their molecular masses are equal

  4. the same number of molecules if their densities are equal.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to avogadro's hypothesis, equal volumes of gases under the same conditions of temperature and pressure will contain, the same no. of molecules.

For eg. One volume of hydrogen combines with one volume of chlorine to produce two volumes of HCl gas.
$H _2\1vol$   $+$  $Cl _2=\1 vol$ $2HCl\2 vol$

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

At constant temperature, in a given mass of an ideal gas:

  1. the ratio of pressure and volume always remains constant

  2. volume always remains constant

  3. pressure always remains constant

  4. the product of pressure and volume always remains constant
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Boyle's Law states that, at constant temperature, the product of the pressure and volume of a given mass of an ideal gas in a closed system, is always constant.