Predict the sign of ΔS^∘ and then calculate ΔS^∘ for each of the following reactions. a. 2 H2 S

step 1 So we have given reactions here. First of all we have 2 H2S gas plus SO2 gas which gives 3 S tha

Predict the sign of ΔS^∘ and then calculate ΔS^∘ for each of...

Predict the sign of $\Delta S^{\circ}$ and then calculate $\Delta S^{\circ}$ for each of the following reactions. a. $2 \mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})+\mathrm{SO}_{2}(\mathrm{~g}) \longrightarrow 3 \mathrm{~S}_{\text {thombic }}(s)+2 \mathrm{H}_{2} \mathrm{O}(g)$ b. $2 \mathrm{SO}_{3}(g) \longrightarrow 2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g)$ c. $\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{Fe}(s)+3 \mathrm{H}_{2} \mathrm{O}(g)$

Predict the sign of $\Delta S^{\circ}$ and then calculate $\Delta S^{\circ}$ for each of the following reactions.
a. $2 \mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})+\mathrm{SO}_{2}(\mathrm{~g}) \longrightarrow 3 \mathrm{~S}_{\text {thombic }}(s)+2 \mathrm{H}_{2} \mathrm{O}(g)$
b. $2 \mathrm{SO}_{3}(g) \longrightarrow 2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g)$
c. $\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+3 \mathrm{H}_{2}(g) \longrightarrow 2 \mathrm{Fe}(s)+3 \mathrm{H}_{2} \mathrm{O}(g)$

Key Concepts

Using Standard Molar Entropy Values in Calculations

Calculating ?S° for a chemical reaction involves using tabulated standard molar entropy values for each reactant and product. The calculation is executed by applying the formula ?S° = ?(n × S°(products)) ? ?(n × S°(reactants)), where n represents the stoichiometric coefficient. This process allows one to quantitatively evaluate whether the reaction leads to an increase or decrease in disorder.

Standard Entropy

Standard entropy refers to the entropy content of a substance measured under standard conditions (usually 1 atm pressure and a specified temperature such as 298 K). It is a measure of the disorder or randomness at the molecular level and is typically provided in units of joules per mole per kelvin (J/(mol·K)). This quantity is a fundamental thermodynamic property that helps in understanding the energy dispersal in chemical processes.

Reaction Entropy Change (?S°)

The reaction entropy change, denoted as ?S°, represents the net change in entropy when reactants are converted into products under standard conditions. It is calculated by subtracting the sum of the standard molar entropies of the reactants from that of the products, taking into account their stoichiometric coefficients. This value helps predict the direction of entropy flow and the spontaneity of a reaction.

Phase Influence on Entropy

The physical state of a substance significantly influences its entropy. Gases generally have much higher entropy than liquids, which in turn have higher entropy than solids, due to the increase in molecular motion and disorder. When predicting ?S°, changes in the number and state of molecules, particularly gases, are critical because they directly impact the overall disorder in the system.

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