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

Verified step by step guidance

1. First, we need to convert ΔH°_rxn from kJ to J because ΔS°_rxn is given in J/K. We can do this by multiplying the given ΔH°_rxn by 1000. So, ΔH°_rxn = +95 kJ * 1000 = +95000 J.
2. Next, we calculate ΔS_univ using the formula ΔS_univ = ΔS°_rxn - (ΔH°_rxn/T). Plug in the given values: ΔS_univ = -157 J/K - (+95000 J/298 K).
3. Calculate the value of ΔS_univ from the above expression.
4. If ΔS_univ is positive, the reaction is spontaneous. If ΔS_univ is negative, the reaction is non-spontaneous.
5. Finally, based on the value of ΔS_univ, predict whether the reaction is spontaneous or not.

Key Concepts

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 a spontaneous reaction, while a positive ΔG suggests non-spontaneity.

Entropy (ΔS)

Entropy (ΔS) is a measure of the disorder or randomness in a system. In the context of a chemical reaction, a positive ΔS indicates an increase in disorder, which favors spontaneity. Conversely, a negative ΔS suggests a decrease in disorder, which can hinder spontaneity. The change in entropy is crucial for determining the overall spontaneity of a reaction when combined with enthalpy changes.

Enthalpy (ΔH)

Enthalpy (ΔH) is a measure of the total heat content of a system and reflects the energy absorbed or released during a reaction. A positive ΔH indicates that the reaction is endothermic, absorbing heat from the surroundings, while a negative ΔH indicates an exothermic reaction, releasing heat. The sign and magnitude of ΔH are essential for evaluating the energy changes that influence the spontaneity of a reaction in conjunction with entropy.