Negative Free Energy - Physical Chemistry

In summary, hydrogen peroxide can be prepared in multiple ways, including the reaction between hydrogen and oxygen and the reaction between water and oxygen. The ΔG°rxn values for each reaction are -120.4 kJ and +116.7 kJ, respectively. Based on these values, it can be determined that the reaction between hydrogen and oxygen (reaction 1) requires less energy under standard conditions compared to the reaction between water and oxygen (reaction 2). This is because a negative ΔG°rxn value indicates a spontaneous reaction, while a positive value indicates a nonspontaneous reaction.
  • #1
cvc121
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Homework Statement


Hydrogen peroxide can be prepared in several ways. One method is the reaction between hydrogen and oxygen, another method is the reaction between water and oxygen. Given the ΔG°rxn values for each reaction, which method (reaction 1 or 2) requires less energy under standard conditions?
1. H2(gas) + O2(gas) <---> H2O2(liquid) ΔG°rxn = -120.4 kJ
2. H2O(liquid) + 1/2 O2(gas) <---> H2O2(liquid) ΔG°rxn = +116.7 kJ

Homework Equations


N/A

The Attempt at a Solution


Would the answer be reaction 2 because it is lower in magnitude? I know that a negative free energy value corresponds to a spontaneous reaction and a positive value a nonspontaneous reaction but is the sign significant in this case?
 
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  • #2
cvc121 said:
Would the answer be reaction 2 because it is lower in magnitude?
No
cvc121 said:
is the sign significant in this case?
Yes
 

1. What is negative free energy?

Negative free energy, also known as Gibbs free energy, is a thermodynamic concept used to determine the amount of energy available to do useful work in a chemical reaction. It is a measure of the spontaneity of a reaction, with a negative value indicating a spontaneous reaction and a positive value indicating a non-spontaneous reaction.

2. How is negative free energy related to entropy?

Negative free energy is related to entropy through the equation ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature, and ΔS is the change in entropy. This equation shows that a decrease in entropy (ΔS < 0) results in a positive value for ΔG, indicating a non-spontaneous reaction. Conversely, an increase in entropy (ΔS > 0) results in a negative value for ΔG, indicating a spontaneous reaction.

3. Can a reaction with negative free energy still be non-spontaneous?

Yes, a reaction with negative free energy can still be non-spontaneous if the change in enthalpy (ΔH) is positive. In this case, the negative value for ΔG is not enough to overcome the positive ΔH, resulting in a non-spontaneous reaction. This is why it is important to consider both ΔH and ΔS when determining the spontaneity of a reaction.

4. What factors affect the value of negative free energy?

The value of negative free energy is affected by temperature, pressure, and the concentrations of reactants and products. Changes in these factors can alter the values of ΔH and ΔS, and therefore affect the overall value of ΔG. Additionally, the standard free energy of formation for each substance involved in the reaction also influences the value of ΔG.

5. How is negative free energy used in practical applications?

Negative free energy is used in various practical applications, such as in the production of electricity through fuel cells and in the design of industrial chemical processes. It is also used in biochemistry and metabolism to determine the energy available for cellular processes. Additionally, negative free energy is used in the study and development of new materials and technologies, such as batteries and solar cells.

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