All Flashcards
What is the formula for calculating Gibbs Free Energy?
ΔG = ΔH - TΔS, where ΔG is Gibbs Free Energy change, ΔH is Enthalpy change, T is Temperature (in Kelvin), and ΔS is Entropy change.
Describe the process of dissolving a substance in terms of enthalpy and entropy.
Energy is needed to break solute-solute and solvent-solvent attractions (endothermic, +ΔH). Forming new solute-solvent attractions releases energy (exothermic, -ΔH). Entropy usually increases as the solute becomes more dispersed in the solution (+ΔS).
How do you determine if the dissolution of a substance is spontaneous?
Calculate ΔG using the formula ΔG = ΔH - TΔS. If ΔG < 0, the dissolution is spontaneous. If ΔG > 0, the dissolution is non-spontaneous.
What is the definition of entropy (ΔS)?
A measure of disorder or randomness in a system; the number of possible arrangements.
What is the definition of Gibbs Free Energy (ΔG)?
A thermodynamic potential that measures the amount of energy available in a chemical or physical system to do useful work at a constant temperature and pressure.
What does a negative ΔG indicate?
A spontaneous (thermodynamically favorable) reaction.
What does a positive ΔG indicate?
A nonspontaneous (thermodynamically unfavorable) reaction.
Define enthalpy (ΔH).
A measure of the heat energy released or absorbed during a chemical reaction.
What does it mean for a reaction to be thermodynamically favorable?
The reaction will proceed forward without needing additional energy input (spontaneous).
What is the effect of increasing temperature on the spontaneity of an endothermic reaction with a positive ΔS?
Increasing temperature makes the reaction more likely to be spontaneous (more negative ΔG).
What is the effect of a large positive ΔH on the solubility of a substance?
A large positive ΔH makes the substance less likely to dissolve spontaneously, especially at lower temperatures.
What is the effect of a large positive ΔS on the solubility of a substance?
A large positive ΔS makes the substance more likely to dissolve spontaneously, especially at higher temperatures.
What happens to entropy during a phase change from solid to gas?
Entropy increases because the molecules have more freedom to move around, leading to greater disorder.
What happens if ΔG = 0?
The reaction is at equilibrium.