Help me solve this

Question

You wanting to develop a new food production technology that combines CO2(g) and H2O(g) directly to form fructose, C6H12O6(s), and O2(g).

a CO2(g) + b H2O(g)  c C6H12O6(s) + d O2(g)

Substance ΔG°f (kJ/mol)

CO2(g) -389.68

H2O(g) -231.16

C6H12O6(s) -1360.10

a. Would you expect that ΔS°rxn for this reaction to be positive or negative? Explain.

b. What is the value of ΔG°rxn for this process?

c. Is energy liberated or consumed in this process? Explain.

d. How many (kilojoules) of energy are required or released to produce 43.628g of fructose by this process?

Answer 1

First, balance the equation:

6CO₂(g) + 6H₂O(g) ==> C₆H₁₂O₆(s) + 6O₂(g) ... balanced equation

a). ∆S would expected to be negative because you begin with 12 mols of gas and end with 6 mols gas. Recall gas has greater entropy than solid, so ∆S should decrease.

b). To find ∆Gº, use the ∆Gº_f values provided and take the difference between the sum of the products and the sum of the reactants:

∑products = (-1360.1) + (6 x 0) = -1360.1 (∆Gº_f for O₂ is zero)

∑reactants = (6 x -389.68) + (6 x -231.16) = (-2338) + (-1387) = -3725

∑products - ∑reactants = -1360.1 + 3725 = 2365 kJ = ∆Gºrxn

c). Energy in this reaction is being consumed because the value of ∆Gºrxn is positive.

d). Energy consumed according to the balanced equation is 2365 kJ / 1 mol C₆H₁₂O₆.

The molar mass of C₆H₁₂O₆ = 180.16 g / mol

mols C₆H₁₂O₆ = 43.628 g x 1 mol / 180.16 g = 0.24216 mols

0.24216 mol x 2365 kJ / mol = 572.7 kJ required