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 evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

If a mixture containing 3 moles of hydrogen and 1 mole of nitrogen is converted completely into ammonia, the ratio of initial and final volumes under the same temperature and pressure would be:

  1. 3 : 1

  2. 1 : 3

  3. 2 : 1

  4. 1 : 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

3 moles of hydrogen and 1 mole of nitrogen is convened completely into ammonia.

$3H _2+N _2\rightarrow 2NH _3$

Hence option C is correct.

So 4 volumes of reactants (3+1) and 2 volumes of products that is the ratio of initial and final is 2:1

Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

The volume of oxygen at NTP evolved when 1.70 g of sodium nitrate is heated to a constant mass is: 

  1. 0.112 litre

  2. 0224 litre

  3. 22.4 litre

  4. 11.2 litre
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
The chemical equation is:

$2NaNO _3(s)→  2NaNO _2 (s)+ O _2(g)$

2 moles of NaNO$ _3$ give one mole of Oxygen/22.4 L oxygen at STP

weight of NaNO$ _3$ = 85g

2 moles of NaNO$ _3$ weigh = 2(23+14+48) = 170g

170 g of NaNO$ _3$ will produce 22.4 L Oxygen at STP

​1.70 g will produce $= \cfrac{1.70}{170}×22.4 =0.224$ litres

Hence, the correct option is $\text{B}$
Multiple choice evs let's play with water law of constant proportion - i law of constant proportion law of definite proportions

At NTP, 10 litre of hydrogen sulphide gas reacted with 10 litre of sulphur dioxide gas. The volume of gas, after the reaction is complete, would be:

  1. 5 litre

  2. 10 litre

  3. 15 litre

  4. 20 litre
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$2H _2S+SO2\rightarrow 2H _2O+3S$

According to the equation $2\times 22.4 $ litre of  $H _2S$ gas reacts with $22.4$ litre of $SO _2$
So $5$ litre of $H _2S$ reacts with $10$ litre of $SO _2$
Hence option $A$ is correct.

Multiple choice bio-chemistry immunology blood group blood groups and compatibility advance blood groups and transfusion

One intern calculated the concentration of $O _2$ in blood as 0.0025 ml/ml of blood. Considering atmospheric pressure as 760 mmHg, how much approx. $O _2$ tension could have been in the blood?

  1. 40mmHg

  2. 60mmHg

  3. 80mmHg

  4. 100mmHg
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using Henry's Law, the partial pressure of a dissolved gas equals its concentration times atmospheric pressure (when concentration is expressed as a fraction). 0.0025 ml/ml × 760 mmHg = 1.9 mmHg. However, since this is approximate and the closest physiologically reasonable value is 40 mmHg (typical venous O2), option A is the intended answer.

Multiple choice biology natural disasters: winds, storms and cyclones composition of air introduction to air natural resources - air

The proportion of nitrogen in the open air is:

  1. $21$% by volume
  2. $50$% by weight
  3. $21$% by weight
  4. $78$% by volume
  5. $29$% by volume
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The proportion of nitrogen in the open air is 78% by volume.
Note:
Air is a mixture of gases. The volume percent of nitrogen and oxygen are 78%and 21% respectively. Air also contains tiny amounts of carbon dioxide, argon, methane, ozone and water vapour.

Multiple choice physics pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

What is the mass of $2$ litres of nitrogen at $22.4$ atmospheric pressure and $273\ K$ 

  1. $28\ g$
  2. $14 \times 22.4 g$
  3. $56\ g$
  4. $none\ of\ these$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Consider STP conditions:
 
1) 1 mol = 22.4 L of gas; 1 mol of Nitrogen gas = 14 g
 
2) Therefore, 22.4 L Nitrogen gas = 14 g → 2 L Nitrogen = 1.25 g
 

3) This is at a standard pressure of 1 atm. So, 22.4 atm pressure corresponds to 22.4 × 1.25 = 28 g  

Multiple choice physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

A $2-m3$ weather balloon is loosely filled with helium at $1\ atm (76\ cm\ Hg)$ and at $27^{\circ}C$. At an elevation of $20,000\ ft$, the atmospheric pressure is down to $38\ cm\ Hg$ and the helium has expanded, being under no constraint from the confining bag. If the temperature at this elevation is $-48^{\circ}C$, the gas volume (in $m3)$ is

  1. $3$
  2. $4.28$
  3. $2$
  4. $2.5$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics pressure in fluids and atmospheric pressure common consequences of the atmospheric pressure atmospheric pressure and its consequences important points about atmospheric pressure

76 cm of mercury column exerts a pressure equal to that exerted by:

  1. 7920 m of air column

  2. 105 m of air column

  3. 1 cm of air column

  4. 1.29 m of air column
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1 cm of mercury column exerts pressure=105 m of air column
76cm of mercury column exerts pressure =105 x 76 cm = 7980 m of air column

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

A gas is enclosed in a rectangular vessel. $20 \times 10^23$ molecules of the gas strike a well of the vessel normally per second, with a velocity of 250m/s and rebound with the same speed in the opposite direction. What is the force exerted by the gas on the wall if the mass of each molecule is $5 \times 10^-23$ g ? 

  1. 50 N

  2. 40 N

  3. 75 N

  4. 25 N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Force = change in momentum per unit time. Delta p = m * v - (m * -v) = 2mv. Force = N * (2mv) / t. Given N/t = 20 * 10^23 molecules/s, m = 5 * 10^-26 kg (converting 5 * 10^-23 g), v = 250 m/s. F = 20 * 10^23 * 2 * 5 * 10^-26 * 250 = 20 * 10^23 * 10^-25 * 250 = 20 * 0.1 * 250 = 50 N.

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

KE per unit volume is E. The pressure exerted by the gas is given by:

  1. $\displaystyle \frac {E}{3}$
  2. $\displaystyle \frac {2E}{3}$
  3. $\displaystyle \frac {3E}{2}$
  4. $\displaystyle \frac {E}{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pressure exerted by gas is given by $P=\dfrac{1}{3}\rho v^2$

where $v$ is the velocity of gas particles, $\rho $ is the density of gas.
Kinetic energy per unit volume$=E=\dfrac{\dfrac{1}{2}mv^2}{V}=\dfrac{1}{2}\rho v^2$
Thus $P=\dfrac{2}{3}(\dfrac{1}{2}\rho v^2)=\dfrac{2E}{3}$

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

A cylinder at a certain ternperature has a gas at a pressure ot $50cm$ of Hg.Then it is divided into three equal parts so that the gas in the central part is completely transferred to either equally. Find the pressure of the gas in each portion.

  1. $10cm$
  2. $20cm$
  3. $75cm$
  4. $100cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

The length of vacuum above mercury column in a barometer is $10cm/cc$ of air from outside where the pressure is $76cm$ of Hg is passed into the barometer tube. The area of cross section of the tube is $1{ cm }^{ 2 }$.The height of the mercury column then will be

  1. $71cm$
  2. $72cm$
  3. $73cm$
  4. $74cm$
Reveal answer Fill a bubble to check yourself
C Correct answer