EXPLANATION
It states that the total pressure of mixture of gas is equal to sum of partial pressure exerted by each individual gases.
MATHEMATICAL EXPLANATION
It can be mathematically expressed as
Ptotal =sum of (Pj) OR
Ptotal=P1+P2+…..+Pn
Where,Ptotal = Total pressure of mixture.
P1,P2,….,Pn are partial pressure of gases.
Dalton’s law of partial pressure can also be expressed in form of mole fraction.
Xi=Pi/Ptotal
Where,Xi=mole fraction of gas ‘i’
Examples
1) In a container a mixture of nitrogen and Oxygen gas are taken. If the partial pressure of nitrogen is 0.25atm and partial pressure of oxygen is 0.52 atm ,then total pressure inside the container will be 0.52 + 0.25 = 0.77atm.
2) We can also calculated the pressure of dry gas by subtracting the pressure of water vapour from total pressure.
The real life example of Dalton’s law of partial pressure is :- When we reach on high altitude of mountain we experience Dalton’s law .As we climb higher, oxygen partial pressure decreases and total atmospheric pressure also decreases. So ,we have to carry oxygen tank while climbing the high altitude mountain.
Question: A mixture of Nitrogen gas & oxygen gas exerts a total pressure of 2 atm on the walls of its container. If the partial pressure of Nitrogen is 2 atm. find the mole fraction of oxygen in the mixture.
Given,
PNitrogen = 2 atm
Ptotal = 3 atm
According to Dalton’s Law = , ptotal = PN + PO
3 = 2 + PO
POxygen = 1 atm
Now, Mole fraction of oxygen i.e. Xo = PO/Ptotal
=) 1/3 = 0.33
Therefore Mole fraction of oxygen is 0.33