Question

Which of the following gases has the highest density at STP?

• A. \( \text{O}_2 \)
• B. \( \text{N}_2 \)
• C. \( \text{CO}_2 \)
• D. \( \text{H}_2 \)

Hint:

Remember: The density of a gas is directly proportional to its molar mass. The higher the molar mass, the higher the density at STP.

Answer 1

The Correct Option is C

Step 1: Recall the concept of molar volume at STP At standard temperature and pressure (STP), one mole of any ideal gas occupies 22.4 L. The density of a gas is given by: \[ \text{Density} = \frac{\text{Mass}}{\text{Volume}} \] Since the volume is constant at STP, the density of a gas depends on its molar mass. Step 2: Compare the molar masses of the gases The molar masses of the gases are: - \( \text{O}_2 \): 32 g/mol, - \( \text{N}_2 \): 28 g/mol, - \( \text{CO}_2 \): 44 g/mol, - \( \text{H}_2 \): 2 g/mol. The gas with the highest molar mass will have the highest density at STP. Answer: Therefore, \( \text{CO}_2 \) has the highest molar mass and, thus, the highest density at STP. So, the correct answer is option (3).