Adipic acid, H2C6H8O4, used to produce nylon, is made commercially by reaction of Cyclohexane (C6H12) and oxygen gas (O2). Please show the work for A-F.

Question

a. write the balanced chemical equation for the given reaction above.

b. is the reaction exothermic or endothermic? Explain.

c. how many grams of Adipic acid will be formed if 25.0g cyclohexane is reacted with 15.0g oxygen gas?

d. what is the limiting reactant? the excess reactant?

e. how much is left unreacted in the chemical reaction?

f. draw a complete enthalpy profile diagram for the above chemical reaction. 

Answer 1

a) _C₆H₁₂ + _O₂ -> _H₂C₆H₈O₄ + _H₂O

Write this as a system of equations:

6 C * w = 6 C * y, this means that w = y

12 H * w = 10 H * y + 2 H * z

2 O * x = 4 O * y + 1 O * z

b) Does this reaction look familiar to you? It should as the textbook example of a combustion reaction is a hydrocarbon being oxidized by oxygen. Are combustion reactions endothermic (taking in heat) or exothermic (releasing heat)? An alternative way of reaching this answer would be using a table of bond energies.

c) This is a limiting reagent problem. First, assume that the reaction is ideal so there are no alternative products being made. Next calculate the molar mass of cyclohexane (6 mol C * 12 g / mol C + 12 mol H * 1 g / mol H) and the molar mass of oxygen gas (2 mol O * 16 g / mol O). Convert grams of reactants into moles of reactants by multiplying the 25.0g of cyclohexane by the reciprocal of the molar mass (25.0g cyclohexane * 1 mol cyclohexane / 84 g cyclohexane). Do the same for the 15 g of oxygen. Once you have moles of each reactant, divide by the coefficient of that reactant species in the balanced chemical equation. Multiply that answer by the coefficient of the product in the balanced chemical equation. Find the reactant that results in the fewest moles of product and use that. Convert the moles of adipic acid back into grams with the molar mass.

d) You will answer this question in solving c.

e) Use the balanced equation to subtract the number of moles of the excess reactant converted into product from the initial mass to get moles of unreacted reactant. Covert this back into grams.

f) I am omitting this for brevity.