Without doing any calculations, determine the sign of ΔSsys for each chemical reaction. a. Mg(s

step 1 So for this problem, we're given a couple of reactions and we need to determine the sign of delt

Without doing any calculations, determine the sign of ΔSsys ...

Without doing any calculations, determine the sign of $\Delta S_{\text {sys }}$ for each chemical reaction. a. $\mathrm{Mg}(s)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{MgCl}_{2}(s)$ b. $2 \mathrm{H}_{2} \mathrm{~S}(g)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(g)+2 \mathrm{SO}_{2}(g)$ c. $2 \mathrm{O}_{3}(g) \longrightarrow 3 \mathrm{O}_{2}(g)$ d. $\mathrm{HCl}(g)+\mathrm{NH}_{3}(g) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(s)$

Without doing any calculations, determine the sign of $\Delta S_{\text {sys }}$ for each chemical reaction.
a. $\mathrm{Mg}(s)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{MgCl}_{2}(s)$
b. $2 \mathrm{H}_{2} \mathrm{~S}(g)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(g)+2 \mathrm{SO}_{2}(g)$
c. $2 \mathrm{O}_{3}(g) \longrightarrow 3 \mathrm{O}_{2}(g)$
d. $\mathrm{HCl}(g)+\mathrm{NH}_{3}(g) \longrightarrow \mathrm{NH}_{4} \mathrm{Cl}(s)$

Key Concepts

Change in the Number of Moles of Gas

In many reactions, the change in entropy is dominated by the change in the number of gaseous molecules. An increase in the number of gas moles generally indicates a positive change in entropy (greater disorder), while a decrease suggests a negative change in entropy (lower disorder). This concept allows for quick predictions of the sign of ?S_sys without detailed calculations.

Entropy as a State Function

Entropy is a thermodynamic property that depends only on the current state of a system, not on how it reached that state. This means that when analyzing reactions, one can determine the overall change in entropy (?S_sys) based solely on the initial and final states of the system without considering the path taken between them.

Phase and Entropy

The phase of a substance greatly influences its entropy because different states of matter have different levels of molecular disorder. Generally, gases have higher entropy than liquids, and liquids have higher entropy than solids, due to the increased freedom of movement and number of accessible microstates in the gaseous phase.

Reaction Stoichiometry and Entropy Change

The stoichiometry of a reaction provides insight into the relative amounts of reactants and products. By comparing the number of moles of substances, particularly gases, on the reactant side to those on the product side, one can infer whether the system’s overall disorder is increasing or decreasing, which directly affects the sign of ?S_sys.

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