Derivation of the Combined Gas Law equation
The three previously defined laws are given as:
- Boyle’s law: PV = k
- Charles law: V/T = k
- Gay-Lussac’s law: P/T = k
Combining three laws we get:
PV/T = k
This is the combined gas law formula,
where
- k is constant,
- V is volume,
- T is temperature,
- P is pressure.
The combined gas law formula can be modified to compare two sets of conditions in a single substance. The initial condition is represented by the values of temperature (T), pressure (P), and volume (V) in the equation with subscripts of ‘i’ . Additionally, the ultimate condition is represented by those with a subscript of ‘f’ .
When the gas is compared in two different conditions, the law can be stated as,
Pi Vi / Ti = Pf Vf / Tf
Where,
- Pi = initial pressure, Vi = initial volume, Ti = initial temperature
- Pf = final pressure, Vf = final volume, Tf = final temperature
It should be noted that the temperature should always be calculated in kelvin. It is therefore necessary to convert the units to kelvin if they are available in the Celsius scale.
Combined Gas Law Formula
Combined Gas Law as the name suggest is combination of different gas laws. The different gas laws that combine to form Combined Gas Law include Boyle’s law, Charles’ Law and Gay Lussac’s law.
In this article, we will learn about combined gas law, its formula and derivation. We will also learn briefly the three gas laws individually.