problem 23, page 245
b. What is the density (in grams per liter) of natural gas at this temperature and pressure?
We just calculated the mass as 6.4 g .
In problem 22 we calculated the volume as 9.6 L.
Density is mass divided by volume, so the density of methane under these conditions is 6.4 g/9.6L or .67 g/L