Thermodynamics Kinetic Theory Gases

1 mole of a gas with γ = 7/5 is mixed with 1 mole of a gas with γ = 5/3, then the value of γ for the resulting mixture is

  1. 2/5
  2. 24/16
  3. 12/7
  4. 7/5

Answer

Use the formula

(n1+n2)/(γ-1) = n1/(γ1-1) + n2/(γ2-1)

(1+1)/(γ-1) = 1/(7/5 - 1) + 1/(5/3 - 1)

2/(γ-1) = 5/2 + 3/2 = 4

(γ-1) = 1/2

γ = 3/2 or 24/16

The correct option is B.