[Physics] single Poisson constant for mixtures of gases

Question

Let's say air consists of 79% nitrogen and 21% diatomic gas. To perform calculations on $\Delta H$ on adiabatic expansions, instead of taking them as individual parts, can I take the air to be a uniform gas with some Poisson constant $\gamma = C_p/C_v$, and if I do that, what would $\gamma$ will be?

Answer 1

Nitrogen is a diatomic gas as well... so the $\gamma$ of air is very close to the $\gamma$ or either oxygen or nitrogen - $$\gamma=\frac75$$

So yes - you should be able to treat air as uniform for your calculation.