If 0.681 g of an unidentified gas is placed in a 442 mL vessel at 49C, it produces a pressure of 0.629 atm. Find the molar mass of the gas.

Answer 1

Use the ideal gas law to find the moles of the gas:

PV = nRT

P = pressure = 0.629 atm

V = volume in liters = 422 ml x 1 L/1000 ml = 0.422 L

n = moles = ?

R = gas constant = 0.0821 Latm/Kmol

T = temperature in Kelvin = 49C + 273 = 322K

Solving for n:

n = PV/RT = (0.629)(0.422)/(0.0821)(322)

n = 0.0100 moles

Now convert moles to molar mass:

0.681 g/0.0100 moles = 68.1 g/mol = molar mass