Question

"When combustion is carried out under controlled conditions in the laboratory, the reaction is highly exothermic, with an enthalpy change (ΔH) of −673kcal/mol. As you know, ΔG for this reaction at 25∘C is −686kcal/mol, so the reaction is also highly exergonic.

What are the values of ΔG, ΔH, and ΔS for the reverse of the above reaction as carried out by a photosynthetic algal cell that is using CO2 and H2O to make C6H12O6? A) ΔG = +686 kcal/mol, ΔH = +673 kcal/mol, ΔS = -ΔG/T
B) ΔG = -686 kcal/mol, ΔH = +673 kcal/mol, ΔS = -ΔG/T
C) ΔG = -686 kcal/mol, ΔH = -673 kcal/mol, ΔS = ΔG/T
D) ΔG = +686 kcal/mol, ΔH = -673 kcal/mol, ΔS = ΔG/T
E) ΔG = 0 kcal/mol, ΔH = 0 kcal/mol, ΔS = 0

Answer 1

The values of ΔG, ΔH, and ΔS for the reverse of the combustion reaction carried out by a photosynthetic algal cell can be determined using the given information. The reverse reaction is exergonic and has ΔG = -686 kcal/mol, ΔH = +673 kcal/mol, ΔS = -ΔG/T.

Step-by-step explanation:

The values of ΔG, ΔH, and ΔS for the reverse of the combustion reaction carried out by a photosynthetic algal cell can be determined using the given information.

1. ΔG is the change in free energy and is equal to -686 kcal/mol for the combustion reaction.
2. ΔH is the change in enthalpy and is equal to -673 kcal/mol for the combustion reaction.
3. ΔS is the change in entropy and can be calculated using the equation ΔG = ΔH - TΔS, where T is the temperature in Kelvin.

In this case, since the reaction is carried out by a photosynthetic algal cell, which is an endergonic process, the reverse reaction would be exergonic. Therefore, the values for the reverse reaction would be:

ΔG = +686 kcal/mol

ΔH = +673 kcal/mol

ΔS = -ΔG/T

So the correct answer is B) ΔG = -686 kcal/mol, ΔH = +673 kcal/mol, ΔS = -ΔG/T