View Available Hints 9 45x103 Correct Part D What mass of ox

View Available Hint(s) 9 45x10-3 Correct Part D What mass of oxygen is needed for the complete combustion of 4 20×10-3 g of methane? Express your answer with the appropriate units. View Available Hint(s) Value Units Submit Provide Feedback DOLL

Solution

moles = mass / molar mass

moles of CH4 = 4.2 x 10-3 g / 16 (g/mol)

moles of CH4 = 2.625 x 10-4 mol

now

the combustion of methane is given by

CH4 + 2 O2 ---> CO2 + 2 H2O

see that

moles of O2 needed = 2.625 x 10-4 mol CH4 x 2 mol O2 / 1 mol CH4

moles of O2 needed = 5.25 x 10-4 mol

now

mass = moles x molar mass

so

mass of O2 needed = 5.25 x 10-4 mol x 32 g/mol

mass of O2 needed = 0.0168 g