2 The volume of a sample of methane CH4 collected over water

2. The volume of a sample of methane (CH4) collected over water at 50.0°C and 711 torr is measured to be 441 mL. Since it was collected over water, the gas sample is a mixture of methane and water vapor. Look up and record the vapor pressure of water at this temperature: a. - b. What is the partial pressure of methane in the gas mixture? c. What is the mole fraction of methane in the gas mixture? d.How many total moles arc in the gas mixture? e. How many moles of methane are in the gas mixture?

Solution

2.

a) vapor pressure of water at 50 c = 92.5 torr

b) partial pressure of methane in the gas mixture = 711-92.5 = 618.5 torr

c) molefraction of methane in the gas mixture = pgas/ptotal

            = 618.5/711

            = 0.87

d) total no of mol of gas = PV/RT

         = ((711/760)*0.441)/(0.0821*323.15)

          = 0.0155 mol

e) No of mol of methane(CH4) in the gas mixture

         = 0.0155*0.87

         = 0.0135 mol