An unknown paraffinic hydrocarbon is defined by the chemical formula CxH2x+2. The paraffin is burned with air, and there is no CO in the combustion products.
(a) Use a degree-of-freedom analysis to determine how many variables must be specified to determine the flow rates of all components entering and leaving the combustion unit. Express the fraction excess air as v and write elemental balances in terms of x, y. and the molar flow rate of CxH2x+2.
(b) Calculate the molar composition of the combustion product gas in terms of x for each of the following three cases: (i) theoretical air supplied (y = 0). 100% conversion of the paraffin; (ii) 20% excess air (y = 0.2), 100% conversion of the paraffin; (iii) 20% excess air. 90(-7( cons ersion of the paraffin.
(c) Suppose x = 3 (i.e. the paraffin is propane). Assuming complete combustion of the hydrocarbon, what is the ratio of CO2 to H2O in the product gas? Use this result to suggest a method for determining the molecular formula of the paraffin.