Question

For ideal gas, which statement is not true

(A) It obeys Boyle’s law
(B) It follows $PV = RT$
(C) Internal energy depends on temperature only
(D) It follows Vander Waal’s equation

Answer 1

Hint: Here out of the four options given below the wrong statement about the ideal gas is being asked. Use the method of elimination, check each option separately if it is true for the ideal gas or not and then eliminate one by one and finally you will get the required answer for the question.


Complete answer:
Let start with option(A):
Boyle’s law is given by, for an ideal gas at constant temperature, the volume of the gas is inversely proportional to the pressure of the gas;
\[V \propto \dfrac{1}{P}\] or \[PV = cons\tan t\]
therefore, ideal gas obeys Boyle’s law during isothermal changes.

Now, for option(B):
We know that the ideal gas law is given by;
$PV = nRT$
This law is for an ideal condition for a gas, hence it holds for ideal gas.

Now, for option(C):
For an ideal gas possesses only kinetic energy and hence the internal energy of the ideal gas depends only on its temperature

At last, for option(D):
As all the above option is already true then automatically the last option must be wrong.
The Vander Waal’s equation is given by;
$\left( {P + \dfrac{{a{n^2}}}{{{V^2}}}} \right)\left( {V - nb} \right) = nRT$
Where, a and b are constant of molecular attraction.
And this equation holds for a particular gas.

Hence the correct answer is Option(D).



Note: Here all the option other than the last one holds for an ideal gas hence we can easily eliminate the wrong statement, also for getting answer in this question you need to know all the basic information about the ideal gas, Boyle’s law and the Vander Waal’s equation and what are the conditions related to it.