find mass and stp

Question

What mass of Neon gas is required to fill an "OPEN" sign if the tube has a volume of 669.1 mL and is filled at STP. Assume ideal gas behavior, and that the gas filling the sign is 100% neon.

Answer 1

At STP, 1 mole of an ideal gas occupies 22.4 liters.

How many liters do we have? 669.1 ml x 1 L/1000 ml = 0.6691 liters

How many moles of Ne do we need? 0.6691 L x 1 mole/22.4 L = 0.0299 moles Ne needed

Mass of Ne needed = 0.0299 moles x 20.2 g/mol = 0.603 g Ne