Question

A sample of gas weighs 4.406g and has a volume of 1100.00 mL at 665.0 torr and 37.0 degrees C. What is the molar mass? Please show work.

Answer 1

Idea gas Equation is PV = nRT

Where

T = Temperature in kelvin = 37.0 oC = 37.0 +273 = 310 K

P = pressure = 665.0 torr

                      = 665.0 / 760 atm                            Since 1 atm = 760 torr

                     = 0.875 atm

n = No . of moles = ?

R = gas constant = 0.0821 L atm / mol - K

V= Volume of the gas = 1100.00 mL

                                 = 1.10 L                    Since 1 L = 1000 mL

Plug the values we get n = PV / RT

                                       = ( 0.875 x 1.10 ) / ( 0.0821 x 310 )

                                       = 0.0378 moles

Given mass of the gas , m = 4.406 g

We have number of moles , n = mass/molar mass

So molar mass of the gas = mass / number of moles

                                        = 4.406 g / 0.0378 mol

                                        = 116.5 g/mol

Therefore the molar mass of the gas is 116.5 g/mol