Entropy Calculation in Chemical Reactions
What is the process to calculate the change in entropy of the universe for a chemical reaction?
To calculate the change in entropy of the universe for a chemical reaction, we need to determine the change in entropy of the system and the surroundings and then add them together.
Calculating ΔS_system
ΔS_system = ΣS(products) - ΣS(reactants) In the given example reaction of 2 CO(g) + O₂(g) → 2 CO₂(g), we have 2 moles of CO₂ as the product. We can substitute the entropies of the products and reactants into the formula to find ΔS_system. Given the entropy values for CO₂, CO, and O₂, we can calculate ΔS_system to be -392 J/mol·K.
Calculating ΔS_surroundings
ΔS_surroundings is the change in entropy of the surroundings and is calculated using the formula:ΔS_surroundings = -ΔH°/T In the reaction, we are given the standard enthalpy change (ΔH°) as -566 kJ and the temperature (T) as 298 K. By substituting these values into the formula, we determine that ΔS_surroundings is 1.9 kJ/K.
Calculating ΔS_universe
Finally, we can calculate the change in entropy of the universe (ΔS_universe) by adding ΔS_system and ΔS_surroundings together. Hence, the formula to calculate ΔS_universe is:ΔS_universe = ΔS_system + ΔS_surroundings By performing the calculations and adding the values of ΔS_system and ΔS_surroundings (-392 J/mol·K and 1.9 kJ/K respectively), we find that ΔS_universe for the given reaction is -392 J/K.