Calculate the number of moles and the mass of gas in 2.50 L of Arat STP. A)56.0 mol, 784 g B)56.0 mol, 2.00 g C)0.112 mol, 0.00279 g D)0.112 mol, 4.47 g E)1.00 mol, 40.0 g

Question

Quizplus · Accepted Answer

At STP (Standard Temperature and Pressure), 1 mole of any gas occupies 22.4 L. Therefore, 2.50 L of Ar gas would contain $2.50 L / 22.4 L/mol = 0.112$ moles. The molar mass of Ar is approximately 40 g/mol, so the mass of 0.112 moles of Ar would be $0.112 mol \times 40 g/mol = 4.48 g$, which rounds to 4.47 g due to significant figures.

Calculate the Number of Moles and the Mass of Gas