Answer to Question #152489 in General Chemistry for Dimple Callangan

Question

10 moles of methane, CH4, is burned in a furnace. If the dry air used in the combustion of methane has no excess, and the flue gas has nitrogen, carbon dioxide, water, and free oxygen, what would be the complete analysis of the flue gas?

Answer 1

CH4 + 4O2 ----> CO2 + 2H2O

To complete burn,

1 mole of CH4, 4 mole of O2 is needed

So, 10 mole of CH4 needs , 40 moles of O2.

According to the reaction 1 mole CH4 produce 1 mole CO2 and 2 mole water.

So, 10 mole CH4 produce 10 mole CO2 and 20 mole water.

We know

The dry air contain 78% Nitrogen

And 21% Oxygen by mole number

In the flue air 40 moles of oxygen gas present. So,

21% = 40 mole

So, 78% = x mole ( say)

x = (40/21)×78 mole

= 148.6 mole

So, 148.6 mole nitrogen gas present in the flue air.

So, the composition is:

148.6 mole nitrogen, 10 mole CO2 and 20 mole water