Which statement is true about the density of air at 20 °C?

Which statement is true about the density of air at 20 °C?

• A. It is about 0.0013 g/cm³ at 20 °C.
• B. It is about 1.0 g/mL.
• C. It is 19.3 g/cm³.
• D. It is 100 g/cm³.

Answer: (A)

Air at room temperature has a very low density. At 20 °C and 1 atm, its density is about 1.2 kilograms per cubic meter, which is 1.2 g per liter. Converting to grams per cubic centimeter gives 0.0012 g/cm^3. So a statement of about 0.0013 g/cm^3 is a solid approximation for air’s density at that temperature. The other values are far too large for a gas like air—for comparison, 1.0 g/mL would be the density of water, while 19.3 g/cm^3 or 100 g/cm^3 correspond to dense solids or metals, not air.

Air at room temperature has a very low density. At 20 °C and 1 atm, its density is about 1.2 kilograms per cubic meter, which is 1.2 g per liter. Converting to grams per cubic centimeter gives 0.0012 g/cm^3. So a statement of about 0.0013 g/cm^3 is a solid approximation for air’s density at that temperature. The other values are far too large for a gas like air—for comparison, 1.0 g/mL would be the density of water, while 19.3 g/cm^3 or 100 g/cm^3 correspond to dense solids or metals, not air.