Ideal gas law Chemistry

Question

1) What is the mass of oxygen gas in a 16.8 L container at 7.00◦C and 5.03 atm?

Answer 1

To find the mass of oxygen, we first need to find the number of moles of oxygen. This is done using the Ideal Gas Law PV = nRT and solving for n (moles)

n = PV/RT

P = pressure = 5.03 atm

V = volume = 16.8 L

R = gas constant = 0.0821 Latm/Kmol

T = temperature in K = 7ºC + 273 = 280K

n = (5.03)(16.8)/(0.0821)(280)

n = 3.68 moles O₂

mass O₂ = 3.68 moles x 32 g/mol = 118 g

Answer 2

The underlying formula that you want to use here is

PV = nRT

In this case since we're solving for the number of moles (n) you want to make that

n = PV / RT

from there then you can plug in the given values and multiply by the molar mass to convert it over!

n = (5.03 atm * 16.8 L) / (0.08206 L*atm / mol * K * 280.15 K) = 3.676 mol

3.676 mol x 32 g/mol = 117.63

meaning that the mass of oxygen gas in the container is 117.63 grams