What is the density of a mixture of 90% air (density air 1.20 kg/m3) and 10% helium (density of 0.180 kg/m3)?

To find the density of the mixture, we need to take into account the proportion of each gas in the mixture and their respective densities.

Step 1: Multiply the density of each gas by its proportion in the mixture.

For air: 0.90 (proportion of air) * 1.20 kg/m3 (density of air) = 1.08 kg/m3

For helium: 0.10 (proportion of helium) * 0.180 kg/m3 (density of helium) = 0.018 kg/m3

Step 2: Add the results together to find the total density of the mixture.

1.08 kg/m3 (contribution of air) + 0.018 kg/m3 (contribution of helium) = 1.098 kg/m3

So, the density of the mixture of 90% air and 10% helium is approximately 1.098 kg/m3.