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 physics option b: engineering physics buoyancy floatation fluid pressure

A thermally insulated cylinder is divided into two equal halves by a thermally insulated wall. One half contains He at 600$\mathrm { K }$ and the other contains $\mathrm { H } _ { 2 }$ at 800$\mathrm { K }$ , pressure being same in two parts equal to $P _ { 0 }$ . Now, the wall is removed and two gases mix. The resulting pressure is

  1. $P _ { 0 }$
  2. 2$P _ { 0 }$
  3. $\frac { 28 P _ { 0 } } { 54 }$
  4. $\frac { 28 P _ { 0 } } { 27 }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Using Dalton's law and energy conservation: P_final = (n_He*R*T_He + n_H2*R*T_H2) / (V_total). Since P0 = nRT/V, n = P0*V/RT. P_final = (P0*V/R*600 * R*600 + P0*V/R*800 * R*800) / (2V) is incorrect. Correct: P_final = (n1+n2)RT_mix / 2V. Using internal energy: (n1Cv1T1 + n2Cv2T2) = (n1Cv1 + n2Cv2)T_mix. For monoatomic (He) Cv=3/2R, diatomic (H2) Cv=5/2R. Result is 28P0/27.

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

Two identical cylinders contain Helium at 2.5atmosphere and Argon at 1 atmosphere respectively. If both gases are transferred in one ofthe cylinders, what is the new pressure? 

  1. $3.5$ atmosphere
  2. $1.5$ atmosphere
  3. $1.75$ atmosphere
  4. $1$ atmosphere.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since the cylinders are identical and we are transferring gases into one, we use Dalton's Law of partial pressures. P_total = P1 + P2 = 2.5 + 1 = 3.5 atm.

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

A box is divided into two equal compartments by a thin partition and they are filled with gases $  P  $and $  Q  $ respectively. The two compartments have a pressure of 250 torr each. The pressure after removing the partition will be equal to

  1. $125 torr$
  2. $2.5 torr$
  3. $250 torr$
  4. $500 torr$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When the partition is removed, the total volume doubles (V + V = 2V). Since the pressure in each was 250 torr, the total moles are proportional to 250*V + 250*V = 500*V. New pressure = 500V / 2V = 250 torr.

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

$28\, gm$ of $N _2$ gas is contained in a flack at a pressure of $10\, atm$ and at a temperature of $57^0$. It is found that due to leakage in the flask, the pressure is reduced to half and the temperature reduced to $27^0 C$. The quantity of $N _2$ gas that leaked out is :-

  1. $\dfrac{11}{20}\, gm$
  2. $\dfrac{20}{11}\, gm$
  3. $\dfrac{5}{63}\, gm$
  4. $\dfrac{63}{5}\, gm$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Using the ideal gas law PV = nRT, we calculate the initial moles of N2 (n1 = P1V1 / RT1) and final moles (n2 = P2V2 / RT2). Since the volume is constant, the ratio of moles is (P2/P1) * (T1/T2). Calculating the difference in moles and converting to mass gives 63/5 grams.

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

The pressure and temperature of an ideal gas in a closed vessel are $720$ kpa and $40^oC$ respectively. If - th of the gas is released from the vessel and the temperature of the remaining gas is raised to $353^oC$, the final pressure of the gas is 

  1. $ 1440$ kPa
  2. $1080$ kPa
  3. $720$ kPa
  4. $ 540$ kPa
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Initial: P1 = 720 kPa, T1 = 313 K. After releasing 1/3 of gas, remaining gas is 2/3 of original: n2 = (2/3)n1. Temperature rises to T2 = 353 + 273 = 626 K. Using P2V = n2RT2: P2 = (n2/n1)(T2/T1)P1 = (2/3)(626/313)(720) = (2/3)(2)(720) = 960 kPa. Wait, this doesn't match. Let me recalculate: if 1/3 is released, remaining is 2/3. Temperature ratio: (353+273)/(40+273) = 626/313 = 2. So P2 = (2/3) × 2 × 720 = 960 kPa. This doesn't match option B (1080 kPa). Perhaps 1/3 remaining means released 2/3? Then P2 = (1/3) × 2 × 720 = 480 kPa. Still no match. Checking if -th means 1/4 released (3/4 remaining): P2 = (3/4) × 2 × 720 = 1080 kPa. Yes! This matches.

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

A container holds $ 10^{26} molecules / m^3 $ each of mass $ 3 \times 10^{-27} $ Kg. Assume that 1/6 of the ,molecule move with  velocity 2000 m/s directly towards one wall of the container while the remaining 5/6 of the molecules move either away from the wall or in perpendicular direction, and all collision of the molecules with the wall or in perpendicular direction, and all collision of the molecules with the wall are elastic.

  1. Number of molecules hitting $ 1 m^2 $ of the wall every second is $ 3 .33 \times 10^{28} $
  2. Number of molecules hitting $ 1 m^2 $ of the wall every second is $ 2 \times 10^{29} $
  3. Pressure exerted on the wall by molecules is $ 24 \times 10^5 Pa. $
  4. Pressure exerted on the wall by moleculaes is $ 4 \times 10^5 Pa, $
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice zoology human influences on the environment carbon cycle ozone layer depletion and causes depletion of ozone layer

At present, the concentration of atmospheric $CO 2$ is ________.

  1. $100$ ppm
  2. $240$ ppm
  3. $380$ ppm
  4. $520$ ppm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
CO2 is a major pollutant of air and a green house gas that contributes to global warming. Concentration of CO2 in the atmosphere is expressed in terms of parts per million or ppm. According to latest research by forecasting systems, CO2 concentration was found to be about 380 ppm which in recent years has increased upto 400 ppm.
So, the correct answer is '380 ppm'.
Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

Which of the following is the density of nitrogen at STP?

  1. $0.33g/L$
  2. $0.65g/L$
  3. $0.80g/L$
  4. $1.25g/L$
  5. $1.60g/L$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

At STP, one mole of any gas occupies 22.4litres of volume. Nitrogen exists in molecular form as $N _2$. 

So, $Denisty= \dfrac{\text Molecular \ mass}{\text Volume}$

Here a Molecular mass of one mole of $N _2$. is 14(2)=28 grams and Volume is 22.4 litres.
So $Denisty= \dfrac{28}{22.4}g/L = 1.25g/L$.
Option D is correct

Multiple choice chemistry separation of matter sedimentation, decantation and filtration other methods of separation separation methods

A $40\ ml$ of a mixture of ${ H } _{ 2 }$ and ${ O } _{ 2 }$ at $18\ ^0C$ and $1\ atm$ pressure was parked so that the for water was complete. The remaining pure gas had a volume of $10\ ml$ at 18 $^0C$ and $1\ atm$ pressure, the remaining gas was ${ H } _{ 2,}$ the mole fraction of ${ H } _{ 2 }$ in the $40\ ml$ mixture is:

  1. $0.75$
  2. $0.5$
  3. $0.65$
  4. $0.85$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the reaction 2H2 + O2 → 2H2O, if 10 ml of H2 remains after complete water formation, then 30 ml of gas reacted. This 30 ml consists of H2 and O2 in 2:1 ratio, so 20 ml H2 + 10 ml O2 reacted. Initial H2 = 20 ml (reacted) + 10 ml (remaining) = 30 ml. Mole fraction = 30/40 = 0.75. The remaining gas is H2, confirming H2 was in excess.

Multiple choice chemistry the periodic table mendeleef's periodic table mendeleev's periodic law and its limitations mendeleev's periodic table development of the modern periodic table into the history

A certain gas takes three times as long to effuse out as helium. Its molecular mass will be :

  1. 27u

  2. 36u

  3. 64u

  4. 9u
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Some gases are taking three times as long to effuse out as helium.

The rate of effusion is always inversely proportional to the square root molecular mass.

The rate of effusion is the ratio of the volume effused to the time taken as follows.

$ \dfrac{{V} _{1}}{{t} _{1}} \times \dfrac {{t} _{2}}{{V} _{2}}$  $=\sqrt {\dfrac{{M} _{{w} _{2}}}{{M} _{{w} _{1}}}}$

 Volume is same, so

$\dfrac{3}{1}= \sqrt{\dfrac{{M _{w2}}}{4}}$

So, $M _{w2} =  36\ unit.$

The molecular mass of the gas is 36 u.

So, the correct option is A.

Multiple choice chemistry man made materials environmental impact: plastics plastic plastic plastic waste garbage in, garbage out

Plastic containers can resist decomposition for:

  1. 50000

  2. 3000

  3. 1000

  4. 40000
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Plastic waste is one of many types of wastes that take too long to decompose. Normally, plastic items can take up to 1000 years to decompose in landfills. But plastic bags we use in our everyday life take 10-1000 years to decompose, while plastic bottles can take 450 years or more.

Multiple choice physics upthrust in fluids, archimedes' principle and floatation applications of floatation principle of floatation and its applications when do objects float on water?

A balloon has volume of 1000 $m^{3}$ . It is filled with hydrogen ($ \rho $ = 0.09 g/L ) . If the density of air is 1.29 g/L , it can lift a total weight of 

  1. 600 kg

  2. 1200 kg

  3. 300 kg

  4. 1800 kg
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Given,
$V _b=1000m^3$
$\rho _h=0.09g/L$
$\rho _a=1.29g/L$
$g=10m/s^2$
Upthrust force = total downward force
$V _b \rho _a h=mg+\rho _h V _b g$
$1000\times 1.29\times 10=mg+0.09\times 1000\times 10$
$1290=mg+90$
$mg=1200kg-weight$
The correct option is B.