± Gibbs Energy: Equilibrium Constant Relation among thermodynamic quantities Cal
ID: 1012800 • Letter: #
Question
± Gibbs Energy: Equilibrium Constant Relation among thermodynamic quantities Calcium oxide, CaO, is manufactured by decomposition of calcium carbonate, CaCO3, in a furnace The thermodynamic properties for a reaction are related by the equation that defines the standard Gibbs energy change of reaction, A,Go, in kJ mol CaCO3 (s)CaO(s) + CO2 (g) The heat produced by a furnace maintained at a temperature of 500 K can decompose calcium carbonate to calcium oxide. The spontaneity of a reaction can be determined from the sign of4, Go . where r is the standard enthalpy change in kJ mol-1 and r S is the standard entropy change in J K-1 mol-1 . A good approximation to the standard Gibbs energy change at any temperature can be obtained by using this equation assuming that A, Ho and ,S change little with temperature Part A Areaction is spontaneous when the Gibbs energy change is less than zero Areaction is nonspontaneous when the Gibbs energy change is greater than zero Areaction is in equilibrium when the Gibbs energy change is equal to zero For the decomposition of calcium carbonate, consider the following thermodynamic data A,H 178.5kJ mol1 AS 161.0K-1 mol-1 Calculate the temperature in kelvins above which this reaction is spontaneous Express your answer to four significant figures and include the appropriate units TValue Units Value Units Submit Hints My Answers Give Up Review PartExplanation / Answer
Part A : Temperature for decomposition of CaCO3
T = dHo/dSo
= 178.5/0.161
= 1108.70 K
So above 1108.70 K the reaction would be spontaneous.
Part B : dGo = dHo - TdSo
at T = 25 + 273 = 298 K
we get,
dGo = 178.5 - 298 x 0.161 = 130.522 kJ/mol
For equilibrium constant,
dGo = -RTlnK
130522 = -8.314 x 298 lnK
Equilibrium constant K = 1.32 x 10^-23
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