Standard Temperature and Pressure mean 273.15 K (00C) temperature and 1 bar (i.e., exactly 105 Pascal) pressure.

 

Standard Ambient Temperature and Pressure (SATP), conditions are also used in some scientific works, SATP conditions mean 298.15 k and 1 bar (i.e. exactly 105 Pa) At SATP (1 bar and 298.15 K), the molar volume of an ideal gas is 24.789 L mol-1.

 

 

ü  Avogadro’s Hypothesis (Volume – Amount Relationship):

It states that equal volumes of all gases under the same conditions of temperature and pressure contain an equal number of molecules. This means that at constant temperature and pressure, the volume of a gas is directly proportional to its number of moles (n) or molecules (N).

Mathematically, it is written as

V α n

V = k4 n

where k4 is a constant

We know that number of moles (n) = mass in gram(w)/molar mass (M)

i.e., n = w/M

So the above equation becomes:

V = k × w/M

Or,     M = k × w/V

Or,     M= k × d

Or,     M α d

i.e., the density of a gas is directly proportional to its molar mass.

 

    ü  Ideal gas: A gas that follows Boyle’s law, Charles’ law and Avogadro law strictly.

 

ü Ideal gas equation or Equation of State:

The combination of the three gas laws (Boyle’s law, Charles’ and Avogadro law) give a single equation which is known as the Ideal Gas Equation.

According to Boyle’s law: V α 1/P     (At constant T and n)

According to Charles’ Law: V α T     (At constant p and n)

According to Avogadro Law: V α n   (At constant p and T)

On combining these three laws we get:

V ∝ n × T × 1/P

Or,   V = R × n × T × 1/P (where R is a constant called Universal Gas Constant)

Or  

PV = nRT........................... (1)

       This equation is known as the Ideal Gas Equation.