Three perfect gasses at absolute temperatures T1, T2 and T3 are mixed. If number of molecules of the gasses are n1, n2 and n3 respectively then temperature of mixture will be (assume no loss of energy)
For perfect gas,
Kinetic Energy of n molecule, K.E=n(12KBT)
Where, KB is Boltzmann constant
If there is no loss of energy.
Total kinetic energy of mixture is sum of each gas kinetic energy.
ntotalK.Etotal=n1K.E1+n2K.E2+n3K.E3
(n1+n2+n3)(12KBT)=n1(12KBT1)+n2(12KBT2)+n3(12KBT3)
T=n1T1+n2T2+n3T3n1+n2+n3