Question

If a gas expands at constant temperature, it indicates that
(A) kinetic energy of the molecule decreases
(B) pressure of the gas increases
(C) kinetic energy of the molecules remains the same
(D) The number of molecules of gas increases.

Answer 1

Gas is one among the fundamental states of matter. Gases are of two types; they are Real gases and ideal gases. Ideal gases will follow all gas laws involving temperature and pressures. Real gases will follow only gas laws only at low pressure and high temperature.

Complete step by step solution:
We must first know what an ideal gas is. The ideal gas is a gas that follows certain rules. First one is that Ideal gases will not attract or repel each other. Second one is Ideal gases do not take up volumes for themselves. The gases that follow the ideal gas equation are called ideal gases. The ideal gas equation is given below:
i.e. $PV = nRT$
where,
P=Pressure of the gas
V=Volume of the gas
n=number of moles of the gas
R=Rydberg constant
T= temperature
The average Kinetic energy of an ideal gas is given as
$K.E = \dfrac{3}{2}RT$
From the above equation we know that R and $\dfrac{3}{2}$ are constant.
Therefore, we can say that Kinetic energy of an ideal gas is directly proportional to Temperature.
$K.E\alpha T$
Therefore, at constant temperature kinetic energy will be the same.

Hence the correct answer is option (C) kinetic energy of the molecules remains the same.

Additional information:

REAL GASES	IDEAL GASES
Real gases obey gas laws at only low pressure and high temperature.	Ideal gases obey all gas laws at all conditions of pressure and temperature.
Volume occupied by molecules are not negligible compared to the total volume of gas.	Volume occupied by molecules are negligible compared to the total volume of gas.
Collisions are inelastic.	Collisions are elastic.
Real gases will obey Van der Waals equation $\left( {P + \dfrac{{a{n^2}}}{{{V^2}}}} \right)\left( {V - nb} \right) = nRT$	Ideal gas will obey ideal gas equation$PV = nRT$

Note: Ideal gases will follow different gas laws such as
- Charles’s law
- Boyle’s law
- Avogadro’s law
- Gay-Lussac’s law