Question

A gaseous fuel mixture consists of 21% propane (C3H8) and 79% butane (C4H10) by volume. Since the total pressure of combustion products is 90 kPa
a) Write the balanced combustion equation for the complete combustion of this fuel mixture. Calculate the theoretical (air-fuel ratio) and dew point temperature of the products.
b) In case of combustion with 200% theoretical air, what is the air fuel rate and dew point temperature?
c) If the air fuel ratio is 20, calculate the number of moles of nitrogen in the air entering the combustion process and the water in the combustion products.

Answer 1

Detailed solution has been given below in the images However, more explanation of C part has been done here.

In the C part,

Mass of air / mass of fuel = 20 {Given}

So, considering for one mol of fuel (molar mass=55g), we can calculate mass of air required for that as,

mass of air required = 55×20 = 1100g.

Therefore, moles of air required,

Na= 1100/29= 37.93 {Molar mass of air = 29g/ mol}

Therefore moles of nitrogen = 0.79×37.93 =29.96 mol.

However, if any doubt or confusion, feel free to put it in comments section, i'll be happy to help you out with that.