Question

1 mole of propane is burned in a combustion chamber with a supply of air that provides the stoichiometrically sufficient amount of Oxygen. However, due to incorrect design of the combustion chamber, only half the Oxygen is actually able to react with propane. Please determine the molar composition and mass composition of the combustion products

Answer 1

the balanced reaction is

C3H8 +   5O2 ---> 3CO2 + 4H2O

1 mol of propane needs 5 moles oxygen gas , since they mentioned we have only half i.e 2.5 moles Oxygen

our product depends on limited moles of oxygen

CO2 moles = ( 3/5) O2 moles = ( 3/5) x 2.5 = 1.5

H2O moles = 4/5 x O2 moles = ( 4/5) x 2.5 = 2 moles

Thus we get 1.5 moles CO2 and 2 moles H2O

Now CO2 mass = moles x molar mass of CO2 = 1.5 x 44 g/mol = 66 g

H2O mass = moles x molar mass of H2O = 2 x 18.015 = 36.03 g