How many atoms of argon are in 58.0 L of argon gas at STP?

Answer 1

At STP 1 mol of ideal gas occupies 22.4 L

58.0 L x 1 mol / 22.4 L = 2.59 moles of Ar

Converting this to atoms, we have...

2.59 moles Ar x 6.02x10²³ atoms/mole = 1.56x10²⁴ atoms