Gaseous State

Using the ideal gas law and the mole ratios from the balanced equation, we calculate the volume fraction of before the reaction as , based on the change in pressure before and after the reaction.

At low pressures, the term becomes negligible and the van der Waals equation simplifies to this expression.
Final Answer:

Step 1: Recall the formula for density of a gas
The density of a gas at STP (Standard Temperature and Pressure) is given by: At STP, the molar volume of any ideal gas is approximately .
Step 2: Compare the molar masses of the gases
- Molar mass of = ,
- Molar mass of = ,
- Molar mass of = ,
- Molar mass of = .
Step 3: Determine the gas with the highest density
Since the density of a gas is directly proportional to its molar mass at STP, has the highest molar mass and hence the highest density at STP. Answer: Therefore, has the highest density at STP. So, the correct answer is option (1).