Chemistry · Physics

Gases and Gas Laws

298 Questions

The study of gases and gas laws involves understanding the relationships between pressure, volume, and temperature of gases. This topic is essential for chemistry and physics sections in many competitive exams. Practice these questions to master concepts like the ideal gas law, partial pressure, and molecular properties.

Ideal gas law calculationsGas volume and pressureStoichiometry of gasesDensity of gasesBoltzmann constant applicationsThermal speed of sound

Gases and Gas Laws Questions

Multiple choice chemistry metals physical properties of metals and non-metals some physical properties of metals general characteristics and uses of metals

Based on the information in each choice below, which of the noble gases would have the greatest density for a $1.00\ L$ sample at room temperature and pressure?

  1. Krypton molar mass $83.8 g/mol$, atomic radius $111$ picometers
  2. Argon molar mass $39.9 g/mol$, atomic radius $94$ picometers
  3. Neon molar mass $20.2 g/mol$, atomic radius $70$ picometers
  4. Helium molar mass $4.0 g/mol$, atomic radius $50$ picometers
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Ans : A Krypton molar mass $83.3\ g/ mol$, atomic radius III picometers.

Note: [ As we go top to bottom, Atomic mass increases. This is because the $e^{\ominus}$ in bigger noble gases are located away from the nucleus and held less tightly by the atom. Therefore the density of krypton is more then $He, Ne$ and $Ar$].

Multiple choice chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

One atmosphere is numerically equal to approximately:

  1. ${ 10 }^{ 6 }\quad dyne\quad { cm }^{ -2 }$
  2. ${ 10 }^{ 2 }\quad dyne\quad { cm }^{ -2 }$
  3. ${ 10 }^{ 4 }\quad dyne\quad { cm }^{ -2 }$
  4. ${ 10 }^{ 8 }\quad dyne\quad { cm }^{ -2 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$P _{dyne/cm^2}=P _{atm}\times 1.01325\times 10^6$


$P _{atm}=1$


then $P _{dyne cm^2}=1.01325\times 10^6$


Option A is Correct.

Multiple choice chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

Which of the following relationships are wrong?

  1. $1 \,atm\approx 0.1 \, bar$
  2. $1 \,liter= 1 \, dm^3$
  3. $1\, J =0.239 \, cal$
  4. $1\, eV =9.11 \times 10^{-4} J$
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

$1\quad atm=1.01325\quad bar\approx 1\quad bar\neq 0.1\quad bar$

$1\quad litre={ 10 }^{ -3 }{ m }^{ 3 }=1{ dm }^{ 3 }$
$1\quad cal =4.18\quad J \Rightarrow 1\quad J =0.239\quad cal\ 1\quad ev=1.6\times { 10 }^{ -19 }J \neq  9.11\times { 10 }^{ -4 }J$
Therefore, $(A). (D)$ are the correct answer.

Multiple choice chemistry matter around us measurement of properties effect of temperature and pressure on states of matter general introduction: importance and scope of chemistry

Which units of pressure are needed if you are going to use 0.0821 as your ideal gas constant?

  1. Atmospheric

  2. Torr

  3. Psi

  4. mmHg

  5. Pascals
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gas constant = $0.0821 $  $L atm K^{−1} mol^{−1}$


atm ( Atmospheric unit is used )

Hence the correct option is A.

Multiple choice

Methane content of biogas is

  1. 24.6%

  2. 55.8%

  3. 8.6%

  4. 4.7%

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biogas is a mixture of gases, primarily methane (50-70%), carbon dioxide, and small amounts of other gases. 55.8% falls within the standard range.

Multiple choice physics temperature and heat modes of heat transfer - conduction conduction heat and modes of heat transfer

Air is filled at $60^o$C in a vessel of open mouth. The vessel is heated at temperature T so that $\dfrac{1}{4}$ th part of air escapes. Assuming volume of container remaining constant, find value of T. 

  1. $80^oC$
  2. $444^oC$
  3. $333^oC$
  4. $171^oC$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Using PV = nRT, since P and V are constant, n1*T1 = n2*T2. If 1/4 escapes, n2 = 3/4 n1. So n1 * (60 + 273) = (3/4)n1 * (T + 273). 333 = 0.75 * (T + 273). 444 = T + 273, so T = 171 C.

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

Consider three identical flasks with different gases:


Flask A: CO at $760$ torr and $273$ K
Flask B: $N _2$ at $250$ torr and $273$ K
Flask C: $H _2$ at $100$ torr and $273$ K

In which flask will the molecules have the greatest average kinetic energy per mole?

  1. A

  2. B

  3. C

  4. Same in all
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Avg kinetic energy$=\dfrac{3}{2}nRT$


$\therefore$ For $1$ mole:-$\dfrac{3}{2}RT$

As the temperature in all of these is same.

$\therefore$ Avg kinetic energy of all these are equal.

Hence, option $D$ is correct.

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

Fill in the blanks:


Component              Inspired air             Expired air
Oxygen                            a                         16.4%
Nitrogen                        79%                        b

  1. a = 5.6%, b = 21.6%

  2. a = 20.96%, b = 79.6%

  3. a = 28.8, b = 98%

  4. a = 1%, b = 2%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Component       Inspired air     Expired air

Oxygen                  20.96%            16.4%
Carbon dioxide       0.04%              4%
Nitrogen                   79%               79.6%

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

The number of air molecules in a $(5m\times5m\times4m)$ room at standard temperature and pressure is of the order of

  1. $6\times10^{23}$
  2. $3\times10^{24}$
  3. $3\times10^{27}$
  4. $6\times10^{30}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Volume V = 5*5*4 = 100 m^3. At STP, 1 mole occupies 22.4 liters (0.0224 m^3). Number of moles n = 100 / 0.0224 approx 4464 moles. Number of molecules = n * Avogadro's number = 4464 * 6e23 approx 2.68e27, which is of the order of 10^27.

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

The ratio of number of collisions per second at the walls of containers by $He$ and $O _2$ gas molecules kept at same volume and temperature, is (assume normal incidence on walls) ?

  1. $2\sqrt{2} :1$
  2. $1:2$
  3. $2:1$
  4. $1:2\sqrt{2} $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The rate of collisions per unit area is proportional to (n * v_avg), where n is number density and v_avg is average speed. Since n = N/V and V, T are same, n is same. v_avg is proportional to 1/sqrt(M). Ratio = v_He / v_O2 = sqrt(M_O2 / M_He) = sqrt(32 / 4) = sqrt(8) = 2*sqrt(2).

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

1 mole of $SO _2$ occupies a volume of $350 ml$ at $300K$ and $50 atm $ pressure. Calculate the compressibility factor of the gas.

  1. $0.888$
  2. $0.711$
  3. $0.520$
  4. $0.987$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given $P=50 \ atm , \ \ V=350 ml =0.350 \ \ \ litre, \ \ n=1 \ \ mole $ and $ T=300 K$

Now, Compressibility factor $Z= \dfrac{PV}{nRT}$
$\therefore  \ Z= \dfrac{50 \times 0.350}{1 \times 0.082 \times 300}= 0.711$

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

If 2g of helium is enclosed in a vessel at NTP, how much heat should be added to it to double the pressure ? (Specific heat of helium = 3 J/gm K)

  1. 1638 J

  2. 1019 J

  3. 1568 J

  4. 836 J
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

No. of moles, $n=\dfrac{m}{M}=\dfrac{2}{4}=0.5 mol$

The specific heat, $C _V=3J/g.mol K$
$C _V=12 J/mol. K$
At constant volume,
$\dfrac{T _2}{T _1}=\dfrac{P _1}{P _2}$
$T _2=2T _1$
$\Delta T=2T _1-T _1=T _1=273K$
The heat required, $\Delta Q=nC _V \Delta T$
$\Delta Q=0.5\times 12\times 273$
$\Delta Q=1638 J$
The correct option is A.

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

The diameter of oxygen molecules is $2.94 \times 10^{-10}m $. The Van der Waals gas constant in m$^3$/mol will be

  1. $3.2$
  2. $32$
  3. $32\times 10^{-6}$
  4. $32 \times 10^{-3}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\displaystyle b = 4N \times \frac{4}{3} \pi \frac{d^3}{8}$ (standard definition of boyles constant)

$\displaystyle = \frac{4 \times 6.02 \times 10^{23} \times 3.14 \times 2.94^3 \times 10^{-30}}{3 \times 8}$

$\displaystyle = 32 \times 10^{-6}$

Multiple choice real gases van der-waal equation: equation of state for real gas kinetic theory of gases thermal physics physics

The size of container B is double that of A and gas in B is at double the temperature and pressure than that in A. The ratio of molecules in the two containers will then be -

  1. $\frac{N _B}{N _A} = \frac{1}{1}$
  2. $\frac{N _B}{N _A} = \frac{2}{1}$
  3. $\frac{N _B}{N _A} = \frac{4}{1}$
  4. $\frac{N _B}{N _A} = \frac{1}{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer