Solid calcium carbonate decomposes according to the reaction CaCO (s) → CaO(s) + CO (g)
CHEMISTRY · Multi-part · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry
Problem
Solid calcium carbonate decomposes according to the reaction
CaCO3(s) → CaO(s) + CO2(g).
A thermochemical study reports ΔH=+178kJmol−1 for the reaction at 25∘C. The accompanying entropy change is reported as ΔS=+160Jmol−1K−1. Assume that the enthalpy and entropy changes are temperature-independent over the range examined.
Answer the following questions about the thermodynamic favorability of this decomposition.
(a) Convert the reported enthalpy change to units consistent with those of the entropy change. Show your work and include appropriate units.
(b) Calculate the value of ΔG for the reaction at 298K. Report your answer with units and correct significant figures.
(c) Based on your result from part (b), determine whether the decomposition is thermodynamically favorable at 298K. Explain your reasoning without using numerical calculations beyond part (b).
(d) Determine the temperature (in Kelvin) at which the reaction becomes thermodynamically favorable under standard-state conditions. Show all algebraic steps.
(e) Limestone kilns typically operate near 1200∘C. Use your result from part (d) to justify why such high temperatures are required industrially, and identify one practical implication this has for energy consumption in cement production.