To good approximation, the thermal conductivity k of a gas (see Ref. 8 of Chap. 1) depends only on the density , mean free path

To good approximation, the thermal conductivity k of a gas (see Ref. 8 of Chap. 1) depends only on the density ρ, mean free path ℓ, gas constant R, and absolute temperature T. For air at 20°C and 1 atm, k ≈ 0.026 W/m⋅K and ℓ ≈ 6.5E−8 m. Use this information to determine k for hydrogen at 20°C and 1 atm if ℓ ≈ 1.2E−7 m.