Question

Which statement about real gases is true? A) Forces of attraction and repulsion exist between gas particles at close range. B) The volume of the gas particles is zero. C) The behavior of real gases can be exactly predicted using the ideal gas law. D) The mass of the gas particles is zero.

Answer 1

Answer: A) Forces of attraction and repulsion exist between gas particles at close range.

Explanation:

The Ideal Gas equation is:  

$P.V=n.R.T$  

Where:  

$P$ is the pressure of the gas  

$V$ is the volume of the gas  

$n$ the number of moles of gas  

$R$ is the gas constant  

$T$ is the absolute temperature of the gas in Kelvin

According to this law, molecules in gaseous state do not exert any force among them (attraction or repulsion) and the volume of these molecules is small, therefore negligible in comparison with the volume of the container that contains them.  In this sense, real gases can behave approximately to an ideal gas, under conditions of high temperature and low pressures.

However, at low temperatures or high pressures, real gases deviate significantly from ideal gas behavior.  This is because at low temperatures molecules begin to move slower, allowing the repulsive and attractive forces among them to take effect. In fact, the attraction forces are responsible for the condensation of the gas. In addition, at  high pressures the volume of molecules cannot be approximated to zero, hence the volume of these molecules is not negligible anymore.