Question

Calculate the change in entropy (ΔS) for the reaction in which 3 moles of carbon monoxide (CO) gas is burned with excess oxygen gas to form 3 moles of carbon dioxide (CO2) gas. The reaction is carried out at constant pressure and a temperature of 298 K.

Answer 1

To calculate the change in entropy  S  for the reaction, we need to find the difference between the entropy of the products and the entropy of the reactants. The reaction is as follows:3 CO g  + 3 O2 g   3 CO2 g First, we need to find the standard molar entropies  S  for each of the gases involved in the reaction. These values can be found in standard thermodynamic tables. The values are:S CO  = 197.7 J/molKS O2  = 205.2 J/molKS CO2  = 213.8 J/molKNext, we calculate the total entropy of the reactants and products:Total entropy of reactants =  3 moles CO  S CO   +  3 moles O2  S O2  Total entropy of reactants =  3  197.7 J/molK  +  3  205.2 J/molK Total entropy of reactants = 593.1 J/molK + 615.6 J/molKTotal entropy of reactants = 1208.7 J/molKTotal entropy of products =  3 moles CO2  S CO2  Total entropy of products =  3  213.8 J/molK Total entropy of products = 641.4 J/molKNow, we can calculate the change in entropy  S  for the reaction:S = Total entropy of products - Total entropy of reactantsS = 641.4 J/molK - 1208.7 J/molKS = -567.3 J/molKThe change in entropy  S  for the reaction is -567.3 J/molK.