The specific heat capacity of a material on a per mass basis is $c = δC/δm$. with $C$ being the heat capacity of a body made of the material and $m$ being the mass of the body.

For gases, there is need to distinguish between different boundary conditions for the processes under consideration. Typical processes for which a heat capacity may be defined include isobaric (constant pressure, d$P = 0$) or isochoric (constant volume, d$V = 0$) processes.

The sources are:

Note: 1 J = 1 W.s

Symbol
$c_{\mathrm{p_{\mathrm{gas}}}}$
Unit
J/kg.K
Formulae
$5.071307038 \cdot 10^{-7} \theta_{\mathrm{air}}^{5} - 8.830478888 \cdot 10^{-5} \theta_{\mathrm{air}}^{4} + 0.0062123003 \theta_{\mathrm{air}}^{3} - 0.1631537093 \theta_{\mathrm{air}}^{2} + 2.05063275 \theta_{\mathrm{air}} + 1004.571427$humid air at 1 atm (Tsilingiris2007)
$1.9327 \cdot 10^{-10} T_{air}^{4} - 7.9999 \cdot 10^{-7} T_{air}^{3} + 0.0011407 T_{air}^{2} - 0.4489 T_{air} + 1057.5$air at 1 atm (Dumas&Trancossi2009)
$0.00039734 T_{air}^{2} - 0.19975 T_{air} + 1030.5$air at 1 bar (UW/MHTL 8406, 1984)
$1.077024 \cdot 10^{-10} T_{air}^{4} - 4.970786 \cdot 10^{-7} T_{air}^{3} + 0.0007816818 T_{air}^{2} - 0.284887 T_{air} + 1034.09$dry air at 1 atm (Irvine&Liley1984)
$0.101 \theta_{\mathrm{gas}} + 1037$N2 (Vermeer1983)
$- 0.00433 \theta_{\mathrm{gas}}^{2} + 1.87 \theta_{\mathrm{gas}} + 630$SF6 (Vermeer1983)
$1.015 T_{\mathrm{gas}} + 539.524$CO2 (linear interpolation)
$1.5 R_{\mathrm{gas}}$Monoatomic ideal gas
$3.5 R_{\mathrm{gas}}$Diatomic molecule gas
$4 R_{\mathrm{gas}}$Polyatomic molecule gas
Related
$R_{\mathrm{gas}}$
$T_{\mathrm{gas}}$
$\theta_{\mathrm{air}}$
$\theta_{\mathrm{gas}}$
Used in
$\alpha_{\mathrm{gas}}$
$\mathrm{Pr}_{\mathrm{gas}}$
$T_{\mathrm{conv_{\mathrm{ce}}}}$
Choices
GasFormula0°C15°C25°C250 K275 K300 K325 K350 K375 K
Air-1005.91006.21006.5
N2N21041.41041.41041.4103910391040104010411042
SF6SF6627.83652.96668.99
CO2CO2826.84841.24850.85791819846871895918
COCO1042.01042.01042.1
O2O2916.72918.22919.62
H2H214197.614267.614306.3
NH3NH32179.52166.22164.5
SO2SO2669.21658.98656.2
HeHe5193.15192.95192.9
ArAr521.85521.65521.55
KrKr249.5249.31249.2
XeXe160.67160.29160.09