Friday, 14 June 2013

Methane burns with stoichiometric quantity of air. The AFR ratio by weight is (a)13. 41

Methane burns with stoichiometric quantity of air. The AFR ratio by weight is
(a)13. 41, (b) 16.79, (c) 12.51, (d) 17.39
Solution: The reaction involved in the combustion of methane is
CH4 + 2O2 à CO2 +2H2O
Molar mass of methane is 16g
Molar mass of 2O2 is 64g
It means, for combustion 16g methane needs 64g O2 OR
1g of methane needs 64/16=4g of O2
Therefore 1kg of methane needs 4kg of O2
Now as we know 23kg of O2 by mass is present in 100kg of air.
Therefore mass of air needed will be (100/23)*4=17.39kg of air
So AFR= Mass of air/Mass of fuel =17.39/1=17.39

So the option (d) is correct

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