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

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.

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

The critical volume of a gas is 0.036 $lit. mol^{-1}$. The radius of the molecule will be (in cm):
(Avogadro Number = $6 \times 10^{23}$)

  1. $\displaystyle \left( \frac{9}{4 \pi} \times 10^{-23} \right)^{\dfrac{1}{3}}$
  2. $\displaystyle \left( \frac{8 \pi}{3} \times 10^{-23} \right)^{\dfrac{1}{3}}$
  3. $\displaystyle \left( \frac{3}{8 \pi} \times 10^{-23} \right)^{\dfrac{1}{3}}$

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

Critical volume of gas=3b [for 1 molecule]

For 1 mole, critical volume=0.036 liters
$\Longrightarrow 0.036\times { 10 }^{ 3 }{ cm }^{ 3 }=3\left( \cfrac { 4 }{ 3 } \pi { r }^{ 3 } \right) \times { N } _{ A } \ \Longrightarrow r={ \left( \cfrac { 36 }{ 24\pi  } \times 10^{ -23 } \right)  }^{ \cfrac { 1 }{ 3 }  }={ \left( \cfrac { 3 }{ 8\pi  } \times 10^{ -23 } \right)  }^{ \cfrac { 1 }{ 3 }  }$

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

According to Avogadro's law the volume of a gas will ____ as _____ if ____ are held constant.

  1. increases, number of moles; P & T

  2. decreases, number of moles; P & T

  3. increases; T & P; number of moles

  4. decreases; P & T; number of moles
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

According to Avogadro's law: Equal volume of all gases at same temperature and pressure will have same no. of molecules.

OR
For a given mass of ideal gas,
Volume$\propto$Number of moles of the gas (if temperature and pressure are constant) 
So, volume of the gas will increase as the number of moles if pressure (P) and temperature (T) are held constant.

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

The critical density of the gas $CO _2$ is 0.44 $g\ cm^{–3}$ at a certain temperature. If $r$ is the radius of the molecule, $r^3$ in $cm^3$ is approximate: 


[N is Avogadro number]

  1. $\cfrac {25} {\pi N}$
  2. $\cfrac {100} {\pi N}$
  3. $\cfrac {6} {\pi N}$
  4. $\cfrac {25} {4N\pi}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Critical density of a gas $= 0.44 gcm^{-3}$
Molar mass of $CO _2$ = 44 g/mole

$Density = mass /volume $
Mass of N molecules = 44 g of $CO _2$    $N =6.022\times 10^{23}$

Mass of 1 molecule $= \dfrac{44}{N}$
The volume of 1 molecule $=\cfrac {4}{3}\pi r^3$
Putting the values,
$ 0.44 = \dfrac{\dfrac{44}{N}}{\cfrac {4}{3}\pi r^3}$

$ r^3 = \dfrac{100}{\pi N}$
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Which facts are revealed from Avogadro's law for ideal gases?

  1. The distance between molecules is much large than the actual dimension of molecules.

  2. Equal number of molecules of different gases under identical conditions of temperatures and pressure occupy the same volume.

  3. Saturated vapours obey gas laws
  4. 1 mole of a gas contains $6.023\times 10^{23}$ molecules of gases.
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation

Avogadro's Law :
It states "equal volumes of any two gases at the same temperature and pressure contain the same number of molecules".

$V  \propto  n$ (At constant P and T)

$\dfrac{V _1}{V _2} = \dfrac{n _1}{n _2}$

and each gas's one mole contains $6.023\times 10^{23}$ molecules.

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

The law which suggests $n _1 = n _2$ for two solutions at same temperature and pressure is 

  1. van't Haff - avogadro's law

  2. van't Hoff Boyle's law

  3. van't Hoff's law

  4. Henry's law
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

van't Hoff's law for osmotic pressure states that for solutions at the same temperature and pressure, the molar concentrations (and thus the number of particles n) are equivalent.

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

Under the same conditions, two gases have the same number of molecules. They must:

  1. be noble gases

  2. have equal volumes
  3. have a volume of 22.4 dm$^3$ each

  4. have an equal number of atoms
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Avogadro's hypothesis: Equal volume of all gases have equal number of molecules (not atoms) at same temperature and pressures conditions.

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

State True or False.
Equal volumes of different gases under similar conditions of temperature and pressure contain equal number of atoms.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The statement, "Equal volumes of different gases under similar conditions of temperature and pressure contain equal number of atoms." is false. The true statement is "Equal volumes of different gases under similar conditions of temperature and pressure contain equal number of moles."  For example, at STP conditions, 22.4 L of any gas corresponds to 1 mole.

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

In the ideal gas equation, the unit of universal gas constant R is?

  1. Mole-atm/K

  2. Litre/mole

  3. Litre-atm/mole.K

  4. erg/K
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In ideal gas equation,


$R=\dfrac{PV}{nT}$ where, 
$P$ is the pressure in 'Atmosphere (atm)'
$V$ is the volume in Litre
$n$ is the number of moles
$T$ is the Temperature in Kelvin (K) 

$ \therefore $Units of $R$= litre.atm/mol.K

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

Which of the following statement about Avogadro's hypothesis is correct?

  1. Under similar conditions of temperature and pressure, gases react with each other in simple ratio.

  2. Under similar conditions of temperature and pressure, equal volumes of all gases contain same number of molecules

  3. At NTP all gases contain same number of molecules

  4. Gases always react with gases only at the given temperature and pressure
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Avogadro’s Law states that under same conditions of temperature and pressure, equal volume of all the gases contain equal number of molecules.

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

Gram molar volume for a gas is always considered at ___ conditions.

  1. NTP

  2. STP

  3. variable temperature

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

Since volume is a dependent variable and it depends on pressure and temperature always so temperature and pressure should be specified when volume of gas is considered. For this certain standard conditions are taken as 273 K and 1 atm pressure.
And at STP, molar volume is 22.4 litre.

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

Two gases A and B which react according to the equation $\displaystyle :aA _{(g)}+bB _{(g)}\rightarrow cC _{(g)}+dD _{(g)}$ to give two gases C and D are taken (amount not known) in an Eudiometer tube (operating at a constant pressure and temperature) to cause the above. If on causing the reaction there is no volume change observed then which of the following statement are correct :

  1. $\displaystyle \:\left ( a+b \right)= \left ( c+d \right )$

  2. Average molecular mass may increase or decrease if either of A or B is present in limited amount.

  3. Vapour Density of the mixture will remain same throughout the course of reaction.

  4. Total moles of all the component of mixture will change.
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Statement 1: At the same temperature and pressure, 1 L of hydrogen gas and  1 L of neon gas have the same mass.
Statement 2: Equal volumes of ideal gases at the same temperature and pressure contain the same number of moles.

  1. <p>Both statement 1 and statement 2 are correct and statement 2 is the correct explanation of statement 1</p>

  2. <p>Both statement 1 and statement 2 are correct but Statement 2 is not the correct explanation of Statement 1</p>

  3. <p>Statement 1 is correct but statement 2 is incorrect</p>

  4. <p>Statement 1 is incorrect but statement 2 is correct</p>

  5. <p>Both the statement 1 and statement 2 are incorrect</p>
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement 1: At the same temperature and pressure, 1 L of hydrogen gas and  1 L of neon gas have the same volume.
Statement 2: Equal volumes of ideal gases at the same temperature and pressure contain the same number of moles.
For example, 1 mole of any gas at STP will occupy a volume of 22.4 L.
Hence, statement 1 is not correct but statement 2 is correct.