1. The problem statement, all variables and given/known data A mixture of gases containing 10 kg of nitrogen, 10 kg of hydrogen, and 15 kg of helium is contained at a pressure of 6.7 MPa and a temperature of 300 K. If the constituents are taken to be perfect gases and the Gibbs-Dalton law holds, what are the molecular weight and specific heat ratio of the mixture? Nitrogen: Mole wt = 28, Specific Heat Ratio = 1.4 Hydrogen: Mole wt = 2 , Specific Heat Ratio = 1.4 Helium: Mole wt = 4, Specific Heat Ratio = 1.67 2. The Attempt at the Solution Basically I first found the number of moles of each constituent by dividing the amount of each constituent in the mixture by its mole weight. Then I found the mole fractions by dividing the # of moles of each constituent by the total number of moles in the mixture. I then multiplied the mole fraction of each constituent by the mole weight for each constituent and divided each by the sum of these products to get the mole fraction of each constituent. This is where I get stuck. To get the specific heat ratio of the mixture I need to determine the specific heat at either constant pressure of volume (doesn't matter which one since you can get the other later on via other relations). How do I determine C_p, for example? I know it depends on temperature, but is there a formula I use to calculate C_p? Where does the pressure of the mixture come into play? Is the fact that the specific heat ratio of each constituent is given trying to hint at something? I guess I am confused as to where to go from here.