# Gaseous State | Measurement Parameters of Gas | Chemistry Grade XI

### Gas State # Gaseous State | Measurement Parameters of Gas

Gaseous State

• It is the simplest form of matter.
• The cohesive force between molecules of a gas is negligible because of this, gas molecules are free to move randomly.

Some measurement parameters of gas:

1. Mass: Mass of gas is measured in terms of gram or kilograms.

2. Mole: It’s  not possible to count the numbers of particles present in definite amount of substances so, quantity of matter is expressed in terms of no. of moles. A mole is amount of substance which has mass equal to gram atomic weight/mass(if the substance is atomic) or gram molecular mass(if the substance is molecular). Mole is denoted by ' n'. Its SI unit is Mol. 1 mole of substance contains 6.023*1023 is called Avogadro’s number( N)

For example,
Atomic mass of carbon=12 gm=1 mole of carbon=6.023 ×1023 no. of carbon atoms.
Atomic mass of sodium=23 gm= 1mole of Na= 6.023×1023 no. of Na atoms.

3. Molar mass: Mass of one mole of substance is called molar mass. It’s unit is g/mol, kg/mol.

For example,
Molar mass of carbon= 12 g/mol
Molar mass of water= 18g/mol

4. Molar Volume: Volume occupied by one mole of substance is called molar Volume. It’s units are l/mol, m3/mol, ml/mol,cm3/mol.
1 mole of gas= 22.4 l [at NTP]

5. Volume: Volume is the space occupied by a body. Gas doesn’t have definite volume. Gas occupies whole volume of container in which it is kept so volume of gas is volume of container at NTP( Normal Temperature Pressure)

Volume occupied by 1 mole of gas at NTP = 22.4L
= 6.023 ×1023 no .of particles

6. Temperature: Temperature of gas is measured in degree celcius(°C). During calculation, degree  Celsius is converted into absolute or degree Kelvin by using following relation:

T = ( t + 273)K
Where,
T= temperature in Kelvin
t= temperature in degree Celsius

7. Pressure: When gas molecules collide with each other or on the wall of container, pressure is exerted. The force exerted by gas molecules per unit area on the wall of container or on the surface where the molecules collide is called gas pressure. The pressure exerted by atmospheric air on the surface of Earth is called atmospheric pressure.

Mathematically,
P= F/ A
= mg/ A [  F= mg]
= dVg/ A [ d= m/V , m= Vd]
= d(A×h )g/ A [ V= A× h]
= dgh

The unit of pressure are: atmospheric pressure, Pascal ( Nm-2), bar, torr, mm of Hg.
1 atm= 760 mmHg
= 760 torr
= 101325 Pa ( Nm-2)
= 105 Pascal
= 1.01325 bar

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