Gaseous State Revision Notes - IIT JEE/NEET Preparation | Nucleon

Gaseous State

• Boyles law
• Statement :
For a fixed amount of gas at constant temperature, the volume occupied by the gas is inversely proportional to the pressure
applied on the gas or pressure of the gas

• Barometer
• A barometer is an instrument that is used for the measurement of pressure.The construction of the barometer is as follows

• Faulty Barometer
• An ideal barometer will show a correct reading only if the space above the mercury column is vacuum, but in case
if some gas column is trapped in the space above the mercury column, then the barometer is classified as a faulty barometer

• Charles law
• For a fixed amount of gas at constant pressure volume occupied by the gas is directly proportional to temperature of the gas on
absolute scale of temperature

• Pay load is defined as the maximum weight that can be lifted by a gas filled balloon.

• Gay-lussacs law
• For a fixed amount of gas at constant volume, pressure of the gas is directly proportional to temperature of the gas on absolute
scale of temperature

• The previous standard is still often used, and applies to all chemistry data more than decade old, in this definition Standard
Temperature and Pressure STP denotes the same temperature of 0°C (273.15K), but a slightly higher pressure of 1 atm
(101.325 kPa

• Daltons law of partial pressure
• In a mixture of non reacting gases partial pressure of any component of gas is defined as pressure
exerted by this component if whole of volume of mixture had been occupied by this component only.
Partial pressure of first component gas

• Analysis of gaseous mixture
• Vapour density :
Vapour density of any gas is defined as the density of any gas with respect to density of the H2 gas under identical conditions of
temperature T and pressure P.

• Diffusion
• Net spontaneous flow of gaseous molecules from region of high concentration (higher partial pressure) to the region of lower
concentration or lower partial pressure

• Kinetic Theory of Gases
• 1  A gas consists of tiny spherical particles called molecules of the gas which are identical in shape & size (mass)
2 The volume occupied by the molecules is negligible in comparision to the total volume of the gas

• Type of velocity
• 1 Root mean square speed :
Urms = U2 =
m
3kT
+ =
mNA
3RT
Where m-mass of one molecule

• Maxwells distributions of molecular speeds
• Postulates/Assumptions of speed distributions

• Real Gases
• 1 Real gases do not obey the ideal gas laws exactly under all conditions of temperature and pressure.
2  Real gases deviates from ideal behaviour because

• Vander Waal Equation of real gases
• The ideal gas equation does not consider the effect of attractive forces and molecular volume.
vander Waal's corrected the ideal gas equation by taking the effect of
(a) Molecular volume (b) Molecular attraction

• VERIFICATION OF VANDER WAALS EQUATIONS
• 1 AT LOW PRESSURE (at separate temp.)
At low pressure Vm will be high.

• Virial Equation of state
• It is a generalised equation of gaseous state. All other equations can be written in the form of virial equation of state.

• Critical constant of a gas
• When pressure increases at constant temperature volume of gas decreases

• Reduced Equation of state
• Reduced Temp : Temperature in any state of gas with respect to critical temp of the gas

• Vapour pressure of a liquid
• Vapour pressure depends on
(a) Temperature (T  VP )
(b) Nature of the liquid

• Eudiometry
• The analysis of gaseous mixtures is called eudiometry. The gases are identified by absorbing them in specified and specific
reagents.

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