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Nikita Parmar

Updated on 31st January, 2023 , 7 min read

What is the difference between Ideal Gas and Real Gas: Definitions, Properties and Similarities

Difference Between Ideal Gas and Real Gas Overview

Solids, liquids, and gases are the three recognized states of matter based on their properties. Because of the strong molecular attraction, solids have distinct masses and structures. Because the molecules in liquids move, they take on the form of a container. The molecules in gases are free to travel wherever they want in the container. There are two types of gas: real gas and ideal gas.

Difference Between Ideal Gas and Real Gas Definitions

Ideal Gas

Ideal gases are gases that follow the ideal gas law at all temperatures and pressures. A theoretical gas is one that does not exist in reality. Because there are no interparticle interactions in an ideal gas, countless minute particles move randomly in all directions. Ideal gases are gaseous mixtures of exceedingly tiny molecules with no volume or mass. However, under high pressure and low temperatures, ideal gases can become actual gases when the gas particles collide with low kinetic energy, resulting in the formation of intermolecular interactions.

Why is an ideal gas thought to be hypothetical?

Every molecule in the cosmos is attracted to another molecule through intermolecular forces. However, in the case of a perfect gas, the molecules do not attract or repel each other. When perfect gas molecules encounter, the only interaction would be an elastic collision or an elastic collision with the container's walls. As a result, in actuality, perfect gas does not exist. It is a fictitious gas invented to make calculations easier.

Real Gas

A true gas is one that defies gas laws under all normal pressure and temperature circumstances. Only at high temperatures and low pressures do real gases obey gas laws. These true gases are composed of discrete atoms or molecules known as particles. There is mass, volume, and velocity in real gases. A gas's volume is defined as the volume of the container in which it is kept. Real gas molecules also have intermolecular interactions. These attraction forces are known as Van Der Waal interactions. When two actual gas particles collide, there is a change in the particle's energy as well as a change in its direction of movement.

Difference Between Ideal Gas and Real Gas Properties

Properties of Ideal Gas

The properties of an ideal gas are as follows-

  1. An ideal gas is made up of many identical molecules.
  2. An ideal gas varies from a real gas in numerous ways. 
  3. The volume filled by the molecules is tiny in comparison to the volume occupied by the gas. 
  4. The molecules move at random despite obeying Newton's laws of motion.
  5. Only when molecules meet do they detect forces; all other collisions are completely elastic and take only a few milliseconds.
  6. For a given temperature, the average kinetic energy of all gases is the same.
  7. Gas molecules that are lighter than heavy molecules travel faster.
  8. Because an ideal gas is referred to as a particle because particles have no mass, the mass of the ideal gas may be omitted in the computation because it does not exist.

Properties of Real Gas

The properties of real gas are as follows-

  1. The composition of a gaseous molecule determines its coefficient of thermal expansion.
  2. The gas-specific coefficient of compressibility was also identified.
  3. A temperature lower than the critical temperature (Tc) permits the molecule to liquefy after a specific pressure, which varies with temperature.
  4. In actual gases, inter-molecular attraction occurs, and when the molecules expand, they must consume more kinetic energy to counteract inter-molecular attraction. 
  5. The temperature lowers as a result.

Difference Between Ideal Gas and Real Gas: Coefficient of thermal expansion and Compressibility

Compressibility of Ideal Gas

The coefficient of compressibility for ideal gases,

β = RT/P2V = 1/P

As a result, pressure should solely be a function of volume and be the same for all gases. However, empirically, the coefficient of compressibility has been discovered to be an individual feature.

Coefficient of thermal expansion of Real Gas

Real gas, unlike ideal gas, has both mass and volume. When it begins to accumulate mass and volume, it departs from its ideal behavior and turns into a true gas. This also demonstrates the distinction between an ideal gas and a real gas.

For one mole ideal gases,

PV = RT

α = R/PV = 1/T

As a result, thermal expansion will be independent of nature and just a function of temperature. The coefficient of thermal expansion of actual gases varies depending on their composition.

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Difference Between Ideal Gas and Real Gas Similarities

The following are some of the similarities between ideal gas and real gas-

Mass: The mass of real and ideal gas particles is the same.

Low density: Gases are denser than liquids or solids. Gas particles are frequently widely separated in both an ideal and a real gas.

Low particle volume: Because gases are not dense, the size or volume of gas particles is relatively small when compared to the distance between particles.

Motion: Kinetic energy is present in both ideal and actual gas particles. Between collisions, gas particles travel at random in a straight path. Because many real gases behave like ideal gases under two circumstances, the ideal gas law is very relevant.

  1. Low Pressure: Many of the gases we come into contact with on a daily basis are at relatively low pressure. It becomes a factor when the pressure is strong enough to force particles into close contact.
  2. High Temperature: In the context of gases, a high temperature is any temperature that is much greater than the vaporization temperature. As a result, actual gas particles have enough kinetic energy to behave like an ideal gas even at ambient temperature.

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Difference Between Ideal Gas and Real Gas 

The following gives the difference between ideal gas and real gas-

Ideal Gas 

Real Gas

There is no specific volume.

Unambiguous volume

Particles collide in an elastic manner.

Particle collisions that are not elastic.

There is no intermolecular attraction force.

The force of intermolecular attraction.

Independently

It interacts with other gases.

Obeys PV = nRT

Obeys P+((n2a)V2)(V−nb)=nRT

It is a hypothetical gas that does not exist in the environment.

It does occur in the environment, albeit at a lower pressure than ideal gas.

The pressure is high.

The pressure is lower when compared to other ideal /perfect perfect gases.

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Key Differences Between Ideal Gas and Real Gas

The table above shows the distinction between real gas and ideal gas. So far, we have assumed that all gases obey the gas laws under all temperature and pressure circumstances; however, this is not the case for actual gases. The distinction between actual gases and ideal gases is that real gases obey gas laws only under certain conditions of low pressure and high temperature.

Real gases deviate from gas laws, and the variations increase as temperature and pressure approach circumstances where the gas may condense into liquid; therefore, the ideal gas equation derived from Boyle and Charles' laws is only useful at relatively low pressures and moderately high temperatures.

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Sample Questions on the Difference Between Ideal Gas and Real Gas

Sample Question 1: How many distinct types of ideal gases exist? 

Ans. There are 3 distinct types of ideal gases that exist which are Classical or Maxwell-Boltzmann equations Ideal Quantum, Ideal Gas Bose gas is composed of bosons and Ideal Quantum Fermi Gas made up of fermions.

Sample Question 2: What exactly is an ideal gas? What exactly is the Ideal Gas Law?

Ans.A perfect gas, also known as an ideal gas, is a hypothetical gas that completely obeys the gas law at all temperatures and pressures.

The Ideal Gas Law states that PV = nRT, which indicates that the product of the pressure and volume of one gram of an ideal gas is equal to the product of the absolute temperature of the gas and the universal gas constant.

Sample Question 3: What exactly is the Z compression factor and what does it imply?

Ans. At constant temperature, the compression factor Z is the ratio of observed molar volume Vm to ideal molar volume V m ideal (= RT/p) as a function of pressure and temperature.

Sample Question 4: What exactly is real gas? Provide examples.

Ans. Real gases are those that do not perfectly obey the ideal gas laws at all temperatures and pressures. Real Gas takes up a certain amount of area and may interact with one another. The following are some frequent Real Gas examples-

  • Nitrogen
  • Oxygen
  • Hydrogen
  • Carbon Dioxide
  • Helium

Sample Question 5: What exactly is a genuine molecule?

Ans. Because real molecules are limited in size and do not overlap, they exhibit intense, short-ranged repulsion. The Pauli exclusion of electrons in the outer orbitals causes the strong, short-ranged repulsion.

Points to Remember

  1. A real gas may be found in nature, but an ideal gas is a made-up gas.
  2. Real gases, on the other hand, obey the gas laws under low pressure and high temperature circumstances, whereas ideal gases do not.
  3. A real gas does not condense when cooled to its boiling point, but an ideal gas does.
  4. An ideal gas has a modest volume in comparison to its whole volume; a real gas, however, has a much larger volume than the ideal gas.
  5. There is no such thing as a "perfect gas," yet genuine gas examples include oxygen, hydrogen, carbon dioxide, and others.
  6. There are no intermolecular forces in a perfect gas. In contrast, intermolecular forces in a real gas can be either attractive or repulsive.

Summary

We went through the definition of an ideal gas in this post. The ideal gas is one in which there are no intermolecular forces of attraction. It also lacks its own volume. Assume that spherical balls are present in close proximity to one another. They do not, however, have any touch with one another. This ideal's particles are free to move. Real gas, on the other hand, is the polar opposite of this. The definitions of "ideal gas" and "real gas" are not the same. A "genuine" gas is one that does not comply with any of the gas laws. It has nothing to do with the Ideal Gas Law. Real gas, unlike ideal gas, has both mass and volume. When it begins to accumulate mass and volume, it departs from its ideal behavior and turns into a true gas. This also demonstrates the distinction between an ideal gas and a real gas. We've covered all of the important points.

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Frequently Asked Questions

Ans. Benoît Paul Émile Clapeyron discovered ideal gas.

Ans. An ideal gas is one that obeys gas laws at all pressure and temperature levels. Ideal gases have mass and velocity. They have no volume.

Ans. No, the ideal gas law does not hold true for liquids.

Ans. A true gas is one that does not obey gas laws under all conventional pressure and temperature circumstances. Real gases have mass, volume, and velocity.

Ans. Three is not an ideal gas. However, at a certain temperature and pressure, a few gases behave like ideal gases.

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