Gas Laws

Boyle’s Law

Boyle’s law states that, “at constant temperature, the pressure exerted by a given mass of a gas is inversely proportional to the volume occupied by it.” If P be the pressure exerted by a gas of volume V, then, at constant temperature,

P ∝ [latex]\frac{1}{V}[/latex]

PV = constant

Let, P₁ and V₁ be the initial pressure and volume of the gas, which is changed to final pressure P₂ and V₂ at constant temperature T, then, Boyle’s law can be written as,

P₁V₁ = P₂V₂ = constant

This is Boyle’s law.

If we plot the graph between P & V, a hyperbolic curve is obtained. Similarly, if we plot the values of P & [latex]\frac{1}{V}[/latex], the following straight line is obtained:

Charles’s law

a.   Charles’s law at Constant Pressure (Law of volume)

It states that, “At constant pressure, the volume of the gas increases or decreases by a constant fraction of the volume at 0^oC for each degree rise or fall in temperature.”

If V_o be the volume of the gas at 0^oC and [latex]V_\theta^oC[/latex] be that at [latex]\theta^oC[/latex] at constant pressure, then, from Charles’s law at constant pressure,