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Standard XII

Chemistry

Avogadro's Law & Gay Lussac's Law

The densities...

Question

The densities of 4 gases at standard temperature and pressure are given in the table
Gas Methane Ammonia Helium Neon
Density 0.72 g/L 0.77 g/L 0.18 g/L 0.90 g/L
Among these gases, which gas diffuses very fast? State the law that helps you to take the decision.

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Solution

According to Graham's law of diffusion, the rates of diffusion, under similar conditions of temperature and pressure, the rates of diffusion of gases are inversely proportional to the square root of their densities.
Helium, with lowest density (0.18 g/L) will have maximum rate of diffusion and will diffuse very fast.

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Similar questions

Q. Details of some gases taken at

273 K

temperature and

1

atm pressure are given in the table.

Gas	Volume (L)	Number of moles
Hydrogen	224	10
Helium	112	5
Oxygen	224	10
Ammonia	56	2.5

(a) On the basis of which gas law, the volume and the number of moles are given in the table?
(b) Represent this gas law in mathematical form.
(c) Among these, if the pressure of hydrogen gas is changed to

2

atm. Calculate the new volume.

Q. According to Graham's law, at a given temperature, the ratio of the rates of diffusion

r_{A} / r_{B}

of gases

A

and

B

is given by :
(Here,

p

and

M

are pressure and molecular weights of gases

A

and

B

, respectively.)

Q. Real gases show deviations from ideal gas law because molecules interact with each other. At high pressures molecules of gases are very close to each other. At very low temperatures intermolecular forces become significant. The deviation from ideal gas behaviour can be measured in terms of compressibility factor

Z

, which is the ratio of product

P V

and

n R T

(

Z = P V / n R T

) . Taking the pressure and volume corrections due to intermolecular forces vander waals corrected the ideal gas equation.
In vander waals equation of state for non ideal gases, the term that accounts for intermolecular forces

Q. According to Graham's law, at a given temperature the ratio of the rates of diffusion

\frac{r_{A}}{r_{B}}

of gases

A

and

B

is given by: (where

p

and

M

are pressures and molecular weights of gases

A

and

B

respectively)

Give reasons for the following:
(a) all temperatures in the absolute (Kelving) scale are in positive figures.
(b) Gases have lower density compared to that of solids or liquids.
(c) Gases exert pressure in all directions.
(d) It is necessary to specify the pressure and temperature of a gas while stating its volume.
(e) inflating a balloon seems to violate Boyle's law.
(f) Mountaineers carry oxygen cylinders with theml.
(g) gas fills completely the vessel in which it is kept.

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Gas	Methane	Ammonia	Helium	Neon
Density	0.72 g/L	0.77 g/L	0.18 g/L	0.90 g/L

The densities of 4 gases at standard temperature and pressure are given in the tableGasMethaneAmmoniaHeliumNeonDensity0.72 g/L0.77 g/L0.18 g/L0.90 g/LAmong these gases, which gas diffuses very fast? State the law that helps you to take the decision.

The densities of 4 gases at standard temperature and pressure are given in the table
Gas Methane Ammonia Helium Neon
Density 0.72 g/L 0.77 g/L 0.18 g/L 0.90 g/L
Among these gases, which gas diffuses very fast? State the law that helps you to take the decision.