This problem set contains 10 chemistry problems involving combustion reactions and calculations. Problem 1 asks to determine air-fuel ratios and product composition for the combustion of dodecane. Problem 2 involves determining air-fuel ratio and fuel composition from an Orsat analysis of an unknown hydrocarbon. Problem 3 requires determining the molecular formula of a fuel given its elemental analysis. The remaining problems involve calculations for various combustion scenarios, such as determining products and temperatures.

1. PROBLEM SET NO. 2
1. Gaseous dodecane, C12H26, is burned completely. Determine (a) the air-fuel ratio
on mass basis; (b) the air-fuel ratio on mole basis; and (c) composition by mass
of the product.
2. The following is the Orsat analysis (dry basis) of an unknown hydrocarbon fuel
when burned with air : CO2 = 11.94%; O2 = 2.26%; CO = 0.41%; N2 = 85.39%.
Determine the air-fuel ratio. What is the gravimetric analysis (%mass of each
element) of the fuel?
3. A fuel has the following ultimate analysis: C, 52.17%; H, 13.05%; O, 34.78 %.
Determine the formula of the fuel.
4. Determine the amount of carbon dioxide produced by the complete combustion
of 5 grams of natural gas (CH4) in stoichiometric air. What is the composition
by mass of the products?
5. Octane burns in air to form carbon dioxide, water, unburned fuel and nitrogen.
Determine the composition of the products in percent mass, if the air-fuel ratio
by mass is 14.5.
6. With 110% theoretical air, 1 kmol of methane is completely oxidized. The
products of combustion are cooled and completely dried at atmospheric
pressure. Determine the (a) partial pressure of oxygen in the products; (b) the
mass, in kilogram, of water removed.
7. Butane is burned in a calorimeter. What is the adiabatic flame temperature if
one gram of gas is burned in theoretical air? Assume that both air and fuel are
fed at 25o
C and 1 atm.
8. Gasoline (C8H18) is burned in a constant volume combustor. Three grams of fuel
is burned with stoich air. The reactants enter the combustor at 25o
C. The heat
loss is 35% of the heat released during combustion. Determine (a) the amount of
energy that remains after the loss; and (b) the temperature of the combustion
products.
9. The reaction of 5 grams of methane in stoich air takes place in an insulated
reactor and the air-fuel mixture enters at 25 o
C and 1 atm. Determine the flame
temperature.
10. Coal with the following as fired composition is burned completely in 110%
theoretical air. C: 80.35%, H: 5.00, O: 4.31%, N: 1.48%, S: 0.86%, moisture:
2.20%, and ash: 5.80%. Determine the heating value of the coal in kJ/kg using
Dulong’s empirical formula. Determine the balanced reaction equation and the
adiabatic flame temperature.