Question

A furnace is fired with petroleum oil containing 50% C, 15% H, 7% S, and the rest is O. Determine the theoretical moles of air required for the combustion of 1 kg of oil.

Answer 1

Firstly we need to find the empirical formula of the fuel

To do that

C H O S

Mass 50 15 28 7

Molar mass 12 1 16 32

Mole=m/mm 50/12 15/1 28/16 7/32

4.17 15 1.75 0.22

Dividing by the smallest mole which is 0.22,

We have our empirical formula to be

C19H68O8S.

So it has to undergo combustion

And the complete combustion of any organic fuel is represented by;

CwHxOySz+1/2[2w+x/2+2z-y]O2----------------------wCO2+x/2H2O+zSO2.

So inputing our values using w=19,x=68,y=8 and z=1

We will have

C19H68O8S+33O2----------19CO2+34H2O+SO2

So now using a mass mole relationship between the fuel and oxygen,we have;

If 33 moles O2 is required for the complete combustion of 456g of the fuel

Then the amount of mole of O2 required for the combustion of 1000g of the fuel is;(the 1kg has been converted to 1000g)

=33×1000/456=72.368moles.