Aerospace Engineering > GATE 2024 > Combustion
A surrogate liquid hydrocarbon fuel, approximated as C10H12, is being burned in a land-based gas turbine combustor with dry air (79% N2 and 21% O2 by volume). How many moles of dry air are required for the stoichiometric combustion of the surrogate fuel with dry air at atmospheric temperature and pressure?
A
61.9
B
30.95
C
13
D
10

Correct : a

The correct answer is Option A: 61.9 moles of dry air.
Let''s work through this carefully. The surrogate fuel given is C10H12, and we need to burn it completely — meaning all the carbon burns to CO2 and all the hydrogen burns to H2O. That''s what stoichiometric combustion means — exactly the right amount of oxygen, no excess, no deficit.
The balanced combustion equation for C10H12 is:
C10H12 + 13 O2 → 10 CO2 + 6 H2O
Here''s how we get the 13: for complete combustion of CxHy, the oxygen required is x + y/4 moles. So for C10H12, that''s 10 + 12/4 = 10 + 3 = 13 moles of O2.
Now, the air provided is dry air — which is 21% O2 and 79% N2 by volume. So if we need 13 moles of O2, the total moles of dry air required is:
Moles of dry air = 13 / 0.21 = 61.9 moles

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Related Topics

GATE 2024 GATE Aerospace Engineering Combustion Stoichiometric Combustion C10H12 Dry Air Moles Gas Turbine Combustor Surrogate Hydrocarbon Fuel Mole Fraction O2 N2 Dry Air GATE AE Q17 Aerospace MCQ GATE Previous Year Questions Combustion Chemistry

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