Question

Which gas sample at STP has the same total number of molecules as 2.0 liters of CO2(g) at STP?
(1) 5.0 L of CO2(g) (3) 3.0 L of H2S(g)
(2) 2.0 L of Cl2(g) (4) 6.0 L of He(g)

Answer 1

The sample at STP that has the same total number of molecules as 2.0 liters of CO2(g) at STP is 2) 2.0 L of CI2 (g)

Answer 2

Avogadro's law states that the volume of a gas is proportional to the number of moles. Also, the number of moles is proportional to the number of molecules (based on Avogadro's constant). Therefore, if 2 gas samples have the same volume, the have the same number of molecules, and the only choice with the same volume of 2.0 L is choice (2).