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
A barometer is an instrument that is used for the measurement of pressure.The construction of the barometer is as follows
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
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.
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
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
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.
Net spontaneous flow of gaseous molecules from region of high concentration (higher partial pressure) to the region of lower
concentration or lower partial pressure
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
1 Root mean square speed :
Urms = U2 =
m
3kT
+ =
mNA
3RT
Where m-mass of one molecule
Postulates/Assumptions of speed distributions
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
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
1 AT LOW PRESSURE (at separate temp.)
At low pressure Vm will be high.
It is a generalised equation of gaseous state. All other equations can be written in the form of virial equation of state.
When pressure increases at constant temperature volume of gas decreases
Reduced Temp : Temperature in any state of gas with respect to critical temp of the gas
Vapour pressure depends on
(a) Temperature (T VP )
(b) Nature of the liquid
The analysis of gaseous mixtures is called eudiometry. The gases are identified by absorbing them in specified and specific
reagents.
