Given the values of ΔH°_rxn, ΔS°_rxn, and T, determine ΔS_univ and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) c. ΔH°_rxn = -115 kJ; ΔS°_rxn = -263 J/K; T = 298 K

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Calculate the change in entropy of the universe (ΔS_univ) using the formula: ΔS_univ = ΔS_rxn + ΔS_surr. Here, ΔS_surr is the change in entropy of the surroundings.

Convert ΔH_rxn from kilojoules to joules to ensure consistency in units for the calculations. Recall that 1 kJ = 1000 J.

Calculate ΔS_surr using the formula: ΔS_surr = -ΔH_rxn / T. This formula arises from the definition of entropy change in the surroundings due to heat transfer at constant temperature.

Substitute the values of ΔH_rxn (converted to joules), ΔS_rxn, and T into the formula to find ΔS_univ.

Determine the spontaneity of the reaction by checking the sign of ΔS_univ. If ΔS_univ is positive, the reaction is spontaneous; if it is negative, the reaction is non-spontaneous.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Gibbs Free Energy

Gibbs Free Energy (G) is a thermodynamic potential that helps predict the spontaneity of a reaction at constant temperature and pressure. It is calculated using the equation ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy. A negative ΔG indicates that a reaction is spontaneous, while a positive ΔG suggests it is non-spontaneous.

Entropy (ΔS)

Entropy (ΔS) is a measure of the disorder or randomness in a system. In the context of chemical reactions, it quantifies the change in disorder as reactants transform into products. A positive ΔS indicates an increase in disorder, which generally favors spontaneity, while a negative ΔS suggests a decrease in disorder, which can hinder spontaneity.

Enthalpy (ΔH)

Enthalpy (ΔH) is a measure of the total heat content of a system and reflects the energy changes during a chemical reaction. A negative ΔH (exothermic reaction) indicates that the reaction releases heat, which can favor spontaneity. Conversely, a positive ΔH (endothermic reaction) absorbs heat, potentially making the reaction non-spontaneous unless compensated by a sufficiently large positive ΔS.

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Textbook Question

Calculate ΔS_surrat the indicated temperature for each reaction. d. ΔH°_rxn= +114 kJ; 77 K

Textbook Question

Given the values of ΔH°_rxn, ΔS°_rxn, and T, determine ΔS_univ and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) a. ΔH°_rxn = +115 kJ; ΔS°_rxn = -263 J/K; T = 298 K

Textbook Question

Given the values of ΔH°_rxn, ΔS°_rxn, and T, determine ΔS_univ and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) c. ΔH°_rxn = +95 kJ; ΔS°_rxn = -157 J/K; T = 298 K

Given the values of ΔH°rxn, ΔS°rxn, and T, determine ΔSuniv and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) c. ΔH°rxn = -115 kJ; ΔS°rxn = -263 J/K; T = 298 K

Verified video answer for a similar problem:

Key Concepts

Gibbs Free Energy

Entropy (ΔS)

Enthalpy (ΔH)

Given the values of ΔH°_rxn, ΔS°_rxn, and T, determine ΔS_univ and predict whether or not each reaction is spontaneous. (Assume that all reactants and products are in their standard states.) c. ΔH°_rxn = -115 kJ; ΔS°_rxn = -263 J/K; T = 298 K