Chemistry · Physics

Gases and Gas Laws

252 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 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 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.
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 $1500\, m^3$. It is filled with hydrogen $(\rho = 0.09\, gL^{-1})$. If the density of air is $1.29\, gL^{-1}$, it can lift a total weight of 

  1. $2400\, kg$
  2. $1600\, kg$
  3. $2700\, kg$
  4. $1800\, kg$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The net upward force (lift) is equal to the difference in weight between the displaced air and the hydrogen gas inside the balloon. Lift = V * (rho_air - rho_hydrogen) = 1500 * (1.29 - 0.09) g/L = 1500 * 1.20 g/L = 1800 kg.

Multiple choice evs atmosphere- wind weather, climate and adaptation of animals to different climates climate and weather weather, climate and adaptations of animals to climate

The $CO _{2}$ content by volume, in the atmospheric air is about

  1. 3.34%

  2. 4%

  3. 0.0314%

  4. 2.1%.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The carbon dioxide present in the atmosphere is generally the result of respiration by animals during the day and the emissions by various vehicles, industries and machines. All these activities account for a total of approximately 0.04% CO2 in the atmospheric air.

So, the correct answer is '0.0314%'.

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

22.4 litres of a gas at STP weighs 16 g. Identify the gas.

  1. Methane

  2. Carbon monoxide

  3. Ethane

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

At STP,  1 mole of gas occupies $22.4l$.

Given gas occupies $22.4l$ at STP and has weight 16 g.
So molecular weight of gas is 16. 
Thus Ans: Methane (Mol. weight of methane is 16)

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

What is the volume occupied by 17.75 g of $Cl _2$ at STP?

  1. $5.6l$
  2. $22.4l$
  3. $11.2l$
  4. $2.8l$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In order to solve this problem, we would use the ideal gas law formula PV = nRT 

at STP standard temp and pressure is 1 atm and 273k

we have 

P = 1atm, n = $\dfrac{17.75}{70.90}$ mole = 0.250, R = $0.0821$ $atm*L/mol*K$ , T=$273K$

V = $\dfrac {nRT}{P}$

= $0.250\times 0.0821\times 273$

= $5.6L$

answer is A


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. How many number molecules does container B have? 

  1. 2N

  2. 4N

  3. N

  4. 8N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Avogadro's law: Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Thus ans is 2N.

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

Assuming that the all volume is measured at the same temperature and pressure, state the volume ratios of the reactants and products for the following gaseous reactions. Nitrogen reacting with oxygen to form nitrogen (III) oxide.

  1. 1 : 3 : 2

  2. 2 : 4 : 2

  3. 2 : 2: 1

  4. 2 : 3 : 2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The equation for the reaction between nitrogen and oxygen to form Nitrogen (lll) oxide is written as:
$2N _{2} + 3O _{2} \rightarrow 2N _{2}O _{3}$
Therefore the volume ratio of reactants and products $= 2 : 3 : 2$

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

Ethane burning in oxygen to give carbon dioxide and steam. The volume ratio of reactants to products is ______________.

  1. 2 : 6 : 4 : 3

  2. 2 : 7 : 2 : 5

  3. 3 : 4 : 4 : 6

  4. 2 : 7 : 4 : 6
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The equation for the combustion reaction of ethane can be written as :
$2C _{2}H _{6} + 7O _{2} \rightarrow 4CO _{2} + 6H _{2}O$
Therefore the volume ratio of reactants and products $= 2 : 7 : 4 : 6$

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

Four one litre flasks are separately filled with gases $O _2, F _2, CH _4$ and $CO _2$ under same conditions. 


The ratio of the number of molecules in these gases are:

  1. $2 : 2 : 4 : 3$
  2. $1 : 1 : 1 : 1$
  3. $1 : 2 : 3 : 4$
  4. $2 : 2 : 3 : 4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Avogadro's law: It states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

$\\ n _{1} : n _{2} : n _{3} : n _{4} = \cfrac{PV}{RT} : \cfrac{PV}{RT} : \cfrac{PV}{RT} : \cfrac{PV}{RT} = 1 : 1 : 1 : 1 $

So, the ratio of no. of molecules $= 1: 1: 1: 1$

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

One gram molecule of any gas at $NTP$ occupies $22.4\ L$. This fact was derived from:

  1. Dalton's theory

  2. Avogardro's hypothesis

  3. Berzelius hypothesis

  4. Law of gaseous volume
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Avogadro's law, 1 mole of every gas occupies 22.4L at $NTP$.

From ideal gas equation,
$PV=nRT$. . . . . . .(1)
At $NTP$,
$T=273K$
$P=1atm$
$n=1$
$R=0.0821atm L/K mol$
from equation (1),
$V=\dfrac{nRT}{P}$
$V=\dfrac{1\times 0.0821\times 273}{1}=22.4L$
The correct option is B.