When the conditions are normal, all gases exhibit similar behaviour. A deviation occurs when physical conditions such as pressure, temperature, or volume change slightly. Gas laws are an examination of how gases behave. The three basic gas laws describe the relationship between pressure, temperature, volume, and amount of gas: Boyle’s Law states the relationship between volume and pressure at constant temperature and mass. Charles’ Law states that the volume of a gas is directly proportional to the temperature at constant pressure and mass. Avogadro’s Law states that all gases have the same number of molecules in their volume at constant temperature and pressure. These three gas laws are combined to form the ideal gas law.

What are Ideal Gases?

The ideal gas, also known as the perfect gas, is a theoretical substance that aids in the determination of the relationship between four gas variables: pressure (P), volume (V), amount of gas (n), and temperature (T). It has the following characters:

1. Because the particles in the gas are so small, the gas takes up no space.
2. The motion of an ideal gas is constant, random, and straight-line.
3. There are no forces between the gas particles. Particles only collide elastically with one another and with the container walls.

What are Real Gases?

On the other hand, real gas has a real volume, and particle collisions are not elastic because there are attractive forces between particles. All real gases exhibit ideal gas behaviour at low pressure and relatively high temperatures. The compressibility factor (Z) indicates how much real gas behaviour differs from ideal. Z=1 for ideal gases. Z≠1 for real gases. Z=PV/nRT

Why are Gas Laws important?

Gas laws are important because they can determine the important parameters of a gas’s mass using theoretical means. The gas laws are applied when comparing two different gases. These laws are also used to determine gas properties.

What is Ideal Gas Law?

The ideal gas law is defined as a simple equation of state that is roughly followed by most gases, particularly at low pressures and high temperatures. For a fixed mole number (n) of almost any gas, the simple equation is related to P (pressure), V (volume), and T (temperature). The ideal gas law is computed as follows: PV=nRT Where n is the number of moles; R is a constant known as the universal gas constant and equal to approximately 0.0821 L-atm / mole-K.

Rules for Using the Ideal Gas Law

• Always convert temperature (T) to kelvins (K).
• Always convert mass (m) to moles (mol).
• Always convert volume (V) to litres (L).
• It is preferable to convert the pressure to Kilopascals (kPa). R, the Universal Gas Constant, is 8.314 (L.kPa)/(mol K).

Boyle’s Law

Boyle’s Law describes the relationship between volume, pressure, and mass at constant temperature and mass. It states that when the pressure on a gas increases under constant temperature, the volume of the gas decreases. In other words, when the temperature and number of molecules are constant, Boyle’s Law states that volume is inversely proportional to pressure.
p ∝ 1/V
p = k₁ 1/V
pV=k₁
Here, k₁ is a proportionality constant, V is volume, and p is pressure. Suppose a fixed mass of gas expands at a constant temperature. In that case, the final volume and pressure are p2 and V₂, p₁, and V1 are the initial volume and pressure.
p₁/p₂=V₂/V₁

Charle’s Law

The volume of a gas is directly proportional to its temperature at constant pressure and constant mass, according to Charle’s Law. This means that as the temperature rises, the volume rises, while as the temperature falls, the volume falls.
V₂/V₁= T₂/ T₁
V/T = constant = k₂
Therefore, V= k₂ T

Avogadro’s Law

At constant temperature and pressure, the volume of all gases equals an equal number of molecules, according to Avogadro’s Law. In other words, under constant temperature and pressure conditions, the volume of any gas is directly proportional to the number of molecules in that gas. V ∝ n Here, n denotes the number of moles of the gas. V=k3n The Avogadro’s constant, calculated to be 6.022 * 10²³, is the number of molecules in a mole of any gas. The temperature and pressure values shown here are the standard values. We’ll use 273.15 K for the temperature and 1 bar or 105 pascals for the pressure.

Conclusion

The gas’s pressure, volume, and temperature are all governed by gas laws. The pressure P of a gas varies inversely with its volume V, or PV = k, at a constant temperature, according to Boyle’s Law, named after Robert Boyle. Avogadro’s Law states that as gas increases, so does the volume. The combination of the three simple gas laws yields the ideal gas law. Charles’ Law states that the volume V is directly proportional to its absolute (Kelvin) temperature T at constant pressure, or V/T = k. These three laws can be combined to form the ideal gas law, PV = nRT, where n is the number of gram-moles in a gas and R is the universal gas constant.