Question

   A sample of gas has a mass of 46.0 g, a pressure of 751 torr, a temperature of 23.0 ?C, and a volume of 70.67 L. You know the gas came from one of five gas tanks in your lab. What is the identity of the gas?

   a) oxygen       b) chlorine       c) methane, CH₄   d) hydrogen       e) argon

Please show work

Answer 1

Ideal gas equation is PV = nRT

                                 PV = (m / M ) RT

Where

P = Pressure = 751 torr = 751/760 atm                Since 1 atm = 760 torr

                                      = 0.988 atm

V = volume = 70.67 L

m = mass of gas = 46.0 g

M = molar mass of gas = ?

R = gas constant = 0.0821 Latm/mol-K

T = temperature in kelvin = 23.0 ^oC = 23.0 + 273 = 296.0K

Plug the values we get

                                  

a) oxygen    --- Molar mass is 32 g/mol

b) chlorine   --- M0lar mass is 71 g/mol   

c) methane, CH₄   --- M0lar mass is 12+(4x1) = 16 g/mol   

d) hydrogen   ---- M0lar mass is 2 g/mol   

e) argon            ----- M0lar mass is 36 g/mol   

So the gas with molar mass 16 g/mol is CH₄(methane)

Therefore the correct option is (c)