A researcher measures the standard Gibbs free energy change for a reaction at four temperatures and obtains the following data:
Temperature T (K) 300 500 700 900
ΔG° (kJ mol⁻¹) −25.1 −8.4 8.3 24.8
(1) On a set of labeled axes that you create, sketch an approximate plot of ΔG° versus T for the data provided. Indicate clearly the region where ΔG° is negative and where it is positive.
(2) Explain why a plot of ΔG° versus T is expected to be linear when ΔH and ΔS are temperature-independent. Using any two convenient data points, estimate the slope and y-intercept of the best-fit line.
(3) Use the slope and intercept determined in part (b) to calculate numerical values for ΔH and ΔS (include units).
(4) Determine the temperature at which the reaction is at equilibrium according to your linear model, and verify that this value is consistent with the sign change observed in the table.
(5) Predict the sign of ΔG° at 1100 K, and explain your reasoning based on the linear relationship.