Real Gas And Equation MCQ - Practice Questions with Answers

• Real gas- The gases which do not obey gas Laws are called Real gas.

Two main factors because of which Real gas deviates from ideal gas are:

1)   Presence of force of attraction between molecules.

2)    The size of molecules is not negligible.

The gases actually found in nature are called real gases.

         From the ideal gas equation, we get 

For exactly one mole of an ideal gas $\frac{PV}{RT}=1$
The quantity $\frac{PV}{RT}$ is called the compressibility factor and should be a unit for an ideal gas.
Plotting the experimentally determined value of $\frac{PV}{RT}$ for exactly one mole of various real gases as a function of pressure $P$    

                shows a deviation from identity as shown in the below graph.

     Similarly, real gases show deviation from ideal behavior as a function of temperature as shown in the below graph.

From the above graphs, we can say that A real gas behaves as an ideal gas most closely at low pressure and high temperature.

• Real gas equation- The real gas equation, For n moles of gas, is given by        

$$(P+\frac{n^{2}a}{V^2})(V-nb)=nRT$$
Where $a$ and $b$ are called Vander wall's constant having dimensions and units as follows:
Dimension : $[a]=\left[M{L}^5{T}^{-2}\right]$ and $[b]=[L]$
Units : $a=N\times m$ and $b=m$

                As we know the ideal gas equation is PV=nRT...... (2)

                From equation (1) and (2) we can say that

          The real gas equation is nothing but the ideal gas equation with two corrections (i.e Volume correction and Pressure correction)

                      These corrections are given by Vander Waal. So the real gas equation is also known as Vander Waal's gas equation.     

 1.  Volume correction-  Due to the finite size of the molecule the effective volume of gas becomes (V –nb).

           2. Pressure correction-  Due to the presence of intermolecular force in real gases, the effective pressure of gas becomes  $P+\frac{n^{2}a}{V^2}$