The reaction of carbon with metal oxide ores is used to isolate metals whenever possible, because carbon is an inexpensive reactant. You are asked to determine the feasibility of using carbon to prepare Ca from lime, which has the formula CaO. The reaction would be

An analysis of the economics shows that the process is practical if the reaction occurs at less than 1500 °C.

(a) Is this reaction spontaneous under standard conditions at 298 K? Use the data in Appendix G.

(b) Estimate the minimum temperature at which this reaction proceeds under standard-state conditions.

(c) In the course of your investigation, you discover that the normal boiling point of calcium is 1484 °C. Estimate the minimum temperature at which this process becomes spontaneous under standard conditions with gaseous calcium as a product.

(d) Can Le Chatelier’s principle be used to decrease the temperature needed to produce calcium by reaction of CaO with graphite? Explain your reasoning.