Ideal Gas

Gas is a collection of particles in rapid motion. The particles are in constant collision all the time. A gas takes up the shape of whatever contains it. An ideal gas has zero interactions among its particles, and it also obeys the ideal gas law. The importance of this concept is that it is used to analyse chemical and engineering calculations.

Ideal gas law states, ‘volume of an ideal gas is directly proportional to the no. of moles of gas and the temperature and inversely proportional to the pressure’. Examples of ideal gases include nitrogen, oxygen, hydrogen and noble gases. The primary use of the ideal gas law is calculating the volume of gas produced or consumed.

Introduction to Ideal Gas

An ideal gas is a theoretical conception of gas having zero interaction between particles. It will only have an elastic collision between the particles. It perfectly obeys the perfect gas law. The internal kinetic energy is kept undisturbed unless there is an increase in temperature or decrease in pressure. All particles have rest mass. Total volume and no. of particles are negligible compared to the system. 

According to IUPAC, one mole of an ideal gas will have a volume of 22.7 litres at 273.15 K temperature and 10⁵ Pa pressure. The concept of an ideal gas is used to analyse other gases in chemical and engineering calculations. The variables associated with an ideal gas are mainly pressure, volume, and temperature.

The ideas of ideal gas law were obtained from combining other three gas laws (Boyle’s law, Charles’s law and Avogadro’s law). Examples of ideal gases include nitrogen, oxygen, hydrogen and noble gases.

Ideal Gas Law

As per ideal gas law, the volume of an ideal gas will be directly proportional to the no. of moles and the temperature and inversely proportional to pressure. This law was obtained by combining three previous gas laws. Ideal gas law is not only applicable to individual gases; it can also apply to a mixture of gases.

Boyle’s law

This law suggests that the pressure of a gas is indirectly proportional to the volume of gas, which can be represented as:

V ∝ 1/P

Charles’s law

This law suggests that the volume of a gas is directionally proportional to the temperature of a gas, assuming pressure is constant, which can be represented as:

V ∝ T

Avogadro’s law

This law suggests the volume of a gas is directly proportional to the number of moles of particles (amount of gas), which can be represented as:

V ∝ n

Combining these three equations, we get

V ∝ nT/P

which gives us,

V = nRT/P

and finally

PV = nRT

where,

P= absolute pressure

V=volume of gas 

n= the amount of gas

T= temperature, and

R= universal gas constant= 8.3145 joules/mol/K

The constant R will have different values in different units. So, when there is a calculation, it should always be ensured that the value of R is in the same unit, which represents other data in question.

Limitations of an Ideal Gas and Ideal Gas Law

• This concept is only applicable in high temperature and low pressure.
• In low temperature and high pressure, gas molecules have little space, interacting more.
• Unlike the ideal gas, real gases do have molecular interactions.

Conclusion

An ideal gas is a theoretical conception of a gas having zero interaction between particles. It will have an elastic collision between the particles. It perfectly obeys the ideal gas law. 

The variables associated with an ideal gas are mainly pressure, volume, and temperature. The ideas of ideal gas law were obtained from combining other three gas laws (Boyle’s law, Charles’s law and Avogadro’s law). However, the ideal gas law is not accurate because gases do not exist in an ideal form in nature, which is a prerequisite for the ideal gas law to be applicable. Natural gases have molecular interactions, and the collisions between the atoms of a gas are not perfectly elastic. It can, however, be used to analyse other gases in engineering and chemical applications.