Free Energy and Temperature

What happens when reactions occur at various temperature? Assume Δ H° and Δ S° remain fairly constant Equilibrium constant and temperature Van Hoff Equation: ln K 2 = Δ H° (1/T 1 - 1/T 2 ) K 1 R Relates equilibrium constant between 2 temperatures

Enthalpy and Entropy Balance Which contributes more to a chemical reaction? Temperature dependent Δ G° = Δ H° - T Δ S°  temperature, Δ S° influences more  temperature, Δ H° influences more

Temperature and Equilibrium Constants Δ G° = -RT lnK Indicates how far a chemical reaction is from equilibrium Temperature dependent.

Temperature and Equilibrium Constants lnK = - Δ H° + Δ S° RT R -focuses on change in temperature - Δ H° > 0, - Δ H°/RT value is negative and makes a small lnK value----increase temperature and lnK becomes larger so - Δ H°/RT value with contribute less - Δ H° < 0, - Δ H°/RT value is positive and larger lnK value results. As temperature increases, - Δ H°/RT value becomes a smaller contribution and lnK decreases

Biological Application Trypsin is an enzyme that breaks peptide bonds holding the amino acids of other proteins together. The equilibrium constant for trypsin denaturation is 7.20 at 50°C. a)Calculate Δ G°. b) Δ H° = +278 kJ/mol. Calculate Δ S° at 50°C c) What does the sign and magnitude of Δ S° tell us about the relationship between trypsin and denatured trypsin? d) Does trypsin denature at 50°C with standard conditions? e) Under standard conditions, what is the maximum temperature trypsin can be stable and not denature?

Homework Finish Thermodynamics II Worksheet Test Study Guide