MCQ Detailed View

At standard temperature and pressure (STP), 1 mole of any ideal gas occupies 22.4 dm³. This rule helps us compare the masses of different gases when they occupy the same volume.

In this question, we are asked: Which gas has the maximum mass in 1 dm³ at STP? Since all gases behave ideally under STP, the deciding factor is the molar mass of each gas.

Let’s examine the options:

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  CO (Carbon monoxide) → molar mass ≈ 28 g/mol

  
  


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  CO₂ (Carbon dioxide) → molar mass ≈ 44 g/mol

  
  


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  C₃H₈ (Propane) → molar mass ≈ 44 g/mol

  
  


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  CS₂ (Carbon disulfide) → molar mass ≈ 76 g/mol

  
  

Since molar mass tells us how many grams are present in one mole (22.4 dm³), we can use this to calculate the mass of 1 dm³ by simple proportion:

Mass in 1 dm³ = (Molar Mass) / 22.4

Based on this, the gas with the highest molar mass will have the highest mass per dm³. CS₂ has the highest molar mass of 76 g/mol. Therefore, it has the greatest density and the largest mass in the given volume of 1 dm³ at STP.

This question is part of core chemistry, particularly involving the behavior of gases under ideal conditions and understanding molar relationships. It demonstrates how density and molecular weight relate to gas behavior in a fixed volume, which is important for understanding gas laws in both academic and real-world applications.