Chemistry ideal gas law help

Question

Calculate the mass of 45L of oxygen gas (O2) having a pressure of 2.43 atm at a temperature of 55oC.

Answer 1

To find the mass of O₂, we first need to find the moles of O₂.

Using the ideal gas law, PV = nRT, we solve for n (moles):

n = PV/RT = (2.43 atm)(45 L) / (0.0821 Latm/Kmol)(328K)

n = 4.06 moles O₂

mass O₂ = 4.06 moles O₂ x 32 g O₂/mol O₂ = 130 g O₂

Answer 2

The underlying formula that you want to use to solve here is

PV = nRT

in this case we're solving that equation for the number of moles (n), so it becomes

n = PV / RT

which for this set of values becomes

n = (2.43 atm x 45 L) / (0.0821 L*atm/mol*K * 328.15 K)

n = 4.06 moles

the final step to convert that over to grams is to multiply by the molar mass

4.06 moles x 32 g/mol = 129.88 grams

meaning that the mass of the oxygen gas here is 129.88 grams