The Properties of Gases at STP: Density, Molar Volume, and Average Speed

Which gas has the highest density at STP?

A. N2
B. O2
C. Ar
D. CO2

Final Answer: At STP, the gas with the highest density is CO2.

At STP (standard temperature and pressure), the density of a gas is directly proportional to its molar mass. This means that the gas with the highest molar mass will have the highest density at STP.

Comparing the molar masses of the gases N2, O2, Ar, and CO2:

  • N2: 28 g/mol
  • O2: 32 g/mol
  • Ar: 40 g/mol
  • CO2: 44 g/mol

Based on the molar masses, we can conclude that CO2 has the highest molar mass and therefore the highest density at STP.

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