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 quantitative chemistry avogadro hypothesis avogadro's law avogadro law

The molecular weights of $O _2$ and $N _2$ are $32$ and $28$ respectively. At $15^0$C, the pressure of $1$gm $O _2$ will be the same as that of $1$ gm $N _2$ in the same bottle at the temperature:

  1. $-21^0$C
  2. $-13^0$C
  3. $15^0$C
  4. $56.4^0$V
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Temperature of $O _{2}$ $=273+15=298 K$

Temperature of $N _{2}$ $=x$

As $n$ $\propto$ $\dfrac 1T$, as pressure is constant.

$\Longrightarrow { n } _{ 1 }{ T } _{ 1 }={ n } _{ 2 }{ T } _{ 2 }\Longrightarrow \left( \cfrac { 1 }{ 32 }  \right) \left( 298 \right) =\left( \cfrac { 1 }{ 28 }  \right) \left( x \right) \\ \Longrightarrow x=\cfrac { 28 }{ 32 } \times 298=260.75K$

Temperature in $^oC=260.75-273=-13 ^oC$

Hence, option $B$ is correct.
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Two gases A and B are taken in same volume containers under similar conditions of temperature and pressure. In container A, there are '2N' molecules of gas A. The number molecules does container B have :

  1. N

  2. 0.5N

  3. 2N

  4. 4N
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
1. According to Avogadro's law, the equal volume of gases under a similar condition of pressure and temperature contain equal no. of molecules. 
Therefore the number of molecules in container B will also be 2N.

2. As we know, one mole of each gas occupies 22.4-litre volume and one mole of gas contains NA molecules at STP.

So at the same temperature and pressure, the equal volume of gas contains equal no of molecules.

Therefore the number of molecules in container B will also be 2N.

Therefore, the option is C.
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

When a certain quantity of oxygen was ozonised in suitable apparatus, the volume decreased by $4\ ml$. On addition of turpentine the volume further decreased by $8\ ml$. All volumes were measured at the same temperature and pressure. From these data, establish the formula of ozone.

  1. $\displaystyle \:O _{3}$
  2. $\displaystyle \:O _{4}$
  3. $\displaystyle \:O _{5}$
  4. $\displaystyle \:O _{6.5}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the formula of ozone be $\displaystyle O _n $
When a certain quantity of oxygen was ozonised in suitable apparatus, the volume decreased by 4 ml.
$\displaystyle  nO _2 \rightleftharpoons 2O _n $
$\displaystyle n-2 \propto 4 $
On addition of turpentine the volume further decreased by 8ml. All volumes were measured at the same temperature and pressure.
$\displaystyle  8mL = 2\times 4mL $
$\displaystyle 2=2n-4 $
$\displaystyle 6=2n $
$\displaystyle  n=3$
Thus, the formula of ozone is $\displaystyle O _3 $.

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

Statement I : At STP, 22.4 liters of He will have the same volume as one mole of $\displaystyle { H } _{ 2 }$ (assume ideal gases).
Statement II : One mole or 22.4 liters of any gas at STP will have the same mass.

  1. true, false

  2. false, true

  3. true, true, correct explanation

  4. true, true, not correct explanation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Avogadro’s law states that under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules. This empirical relation can be derived from the kinetic theory of gases under the assumption of a perfect (ideal) gas. The law is approximately valid for real gases at sufficiently low pressures and high temperatures.
At STP, all gas have same volume for 1 mol of gas and that volume is always equal to the 22.4 L.  

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

The residual pressure of a vessel at ${27^0}C$ is  $1 \times {10^{ - 11}}N/{m^2}$. The number of molecules in this vessel is nearly:

  1. $2400$
  2. $2.4 \times {10^9}$
  3. ${10^{ - 11}} \times 6 \times {10^{23}}$
  4. $2.68 \times {10^{19}} \times {10^{11}}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using the ideal gas law PV = NkT, where P = 10^-11, T = 300K, and k = 1.38 * 10^-23. For a unit volume (1 m^3), N = P / kT = 10^-11 / (1.38 * 10^-23 * 300) approx 2.4 * 10^9.

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

One atmospheric pressure (atm)  is equal to

  1. 101325 Pa

  2. 1013.25 Pa

  3. 101.325 Pa

  4. 10.1325 Pa
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

One Pascal is the pressure exerted by a force of one newton, normally on an area of one square meter.

Atmospheric pressure is the force per unit area by the weight of air on a point.
One atmospheric pressure is related with the Pascal as:
    $1atm=101325Pa$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

'The atmospheric pressure at a place is $76  cm$ of $Hg$? State its value in $bar$.

  1. $1.013\times{10}^{5}$ $bar$
  2. $1 bar$
  3. $1.013\times{10}^{-5}$ $bar$

  4. None
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$1atm$ is the standard atmospheric pressure. 
In terms of length of mercury it is $76cm $ of Hg.

In SI units, the atmospheric pressure is $1atm=1.01325\times 10^{5}Nm^{-2}= 1 bar$

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

Fill in the blanks:
1 psi is equivalent to $-$ atmospheric pressure.

  1. $34.046\times 10^{-3}$
  2. $64.046\times 10^{-6}$
  3. $24.046\times 10^{-3}$
  4. $68.046\times 10^{-3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Psi stands for pound force per square inch. 

Normal atmospheric pressure is 14.7psi.
         $14.7psi=1$ atmospheric pressure

         $1psi=68.027\times10^{-3}atm$