The density of a gas is 1.41 g at STP. What is the gas? A) Cl₂ B) NH₃ C) O₂ D) Ne

Question

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The molar mass of a gas can be calculated using the ideal gas law: PV = nRT. At STP (standard temperature and pressure), P = 1 atm and T = 273 K. Therefore, the equation becomes: V = nRT/P Assuming 1 mole of gas occupies 22.4 L at STP, we can solve for n: n = PV/RT = (1 atm)(22.4 L)/(0.08206 L•atm/mol•K)(273 K) = 1 mol The molar mass can then be calculated as the mass of 1 mole of the gas: molar mass = mass/moles = 1.41 g/1 mol = 1.41 g/mol The only gas with a molar mass close to 1.41 g/mol is carbon monoxide (CO), which has a molar mass of 28.01 g/mol. However, the options don't include CO. The next closest gas is carbon dioxide (CO2), which has a molar mass of 44.01 g/mol. Oxygen (O2) and nitrogen (N2) are much lighter with molar masses of 32 g/mol and 28 g/mol, respectively. The only gas that has a molar mass close to 1.41 g/mol and is an option is O₂ (carbon dioxide). Therefore, the answer is C).

The Density of a Gas Is 1