Question 1
Paper 2Hard12 marksCalcium oxide is produced by heating limestone, which contains calcium carbonate. The standard Gibbs energy change, for the decomposition is shown in Figure 1. Assume that and remain constant over the temperature range shown.
Write a balanced equation, including state symbols, for the thermal decomposition of calcium carbonate.
Use Figure 1 to estimate at
Use Figure 1 to determine and for the decomposition. Give signs and units, and show how you obtain both values.
Using your values from (c), determine the temperature at which State at which temperatures the forward decomposition is spontaneous under standard-state conditions.
At a gas stream keeps the carbon dioxide partial pressure in the kiln at For the reaction as written, take
with pure solids omitted from Under these conditions,
where
Determine the carbon dioxide partial pressure at which at Hence decide whether the forward decomposition is spontaneous at and assess the claim that a positive at means that the decomposition cannot be spontaneous.