Free energy change

Definition

Free energy change is a thermodynamic quantity that represents the difference in free energy between reactants and products in a chemical reaction, indicating the spontaneity of the reaction. It combines both enthalpy and entropy considerations to determine whether a reaction can occur naturally under constant temperature and pressure conditions. A negative free energy change suggests that the reaction is spontaneous, while a positive value indicates non-spontaneity.

5 Must Know Facts For Your Next Test

1. In step-growth polymerization, free energy change helps predict the formation of polymers from monomers by assessing if the process will occur spontaneously.
2. The relationship between free energy change (ΔG), enthalpy (ΔH), and entropy (ΔS) is expressed by the equation: $$ ext{ΔG} = ext{ΔH} - T ext{ΔS}$$, where T is the absolute temperature.
3. Negative values of free energy change during polymerization indicate that products are more stable than reactants, favoring polymer formation.
4. The kinetics of step-growth polymerization can also be influenced by free energy changes; lower activation energies correlate with more favorable free energy profiles.
5. Understanding free energy change is crucial for designing reactions in polymer science to optimize yield and control molecular weight.

Review Questions

• How does free energy change influence the spontaneity of step-growth polymerization reactions?
  • Free energy change directly influences the spontaneity of step-growth polymerization by indicating whether the reaction can proceed without external energy input. If the free energy change is negative, it means that the formation of the polymer from monomers is thermodynamically favorable, leading to spontaneous reactions. Conversely, a positive free energy change suggests that additional energy would be needed to drive the reaction forward, making it non-spontaneous.
• In what ways does the relationship between enthalpy and entropy affect the free energy change during polymerization processes?
  • The relationship between enthalpy and entropy is critical in determining free energy change during polymerization processes. Enthalpy reflects heat changes associated with bond formation or breaking, while entropy measures disorder in the system. A favorable polymerization reaction may have low enthalpy changes (exothermic) and increased entropy as monomers combine into larger structures, resulting in a negative free energy change. Thus, both factors must be balanced for optimal polymer formation.
• Evaluate how controlling temperature could optimize the free energy change in step-growth polymerization and impact final polymer characteristics.
  • Controlling temperature can significantly optimize free energy change in step-growth polymerization by influencing both enthalpy and entropy. An increase in temperature typically enhances molecular motion, which can lead to greater entropy as more configurations become accessible. This can result in a more favorable free energy change if it compensates for any unfavorable enthalpic contributions. Consequently, managing temperature not only affects the spontaneity of the reaction but also impacts final polymer characteristics like molecular weight and branching, allowing for tailored material properties.

Related terms

Gibbs Free Energy: A thermodynamic potential that measures the maximum reversible work obtainable from a closed system at constant temperature and pressure, crucial for determining spontaneity.

Enthalpy: A measure of the total heat content of a system, important for understanding the heat changes during a reaction.

Entropy: A measure of disorder or randomness in a system, which plays a critical role in determining the spontaneity of reactions.