An ideal gas in a 1.25-gallon container is at a temperature of 125 degrees Celsius and pressure of 2.5 atmospheres. If the gas is oxygen (formula:O2 molecular weight = 32 grams per mole), what is the mass of gas in the container in units of grams?

You will need the equation PV = nRT

P = Pressure in kPa

V = Volume in L

n = moles

R = 8.314 (constant)

T = Temperature in Kelvin

First convert 2.5 atm into kPa:

2.5 X 101.3 = 253.25 kPa

Convert 125 Celsius into Kelvin:

125 + 273 = 398 K

Convert Gallons to Litres:

1.25 X 3.79 = 4.74 L

Plug your values into the equation to solve for n:

(253.25) (4.74) = n (8.314) (398)

n = (253.25) (4.74) / (8.314) (398)

n = 0.362 moles

Now use M = m/n to solve for the mass of O2

M = Molar Mass

M = mass

n = moles

32 = m / (0.362)

m = (32) (0.362)

m = 11.58g