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Zorluk: KolayEntropy, Free Energy and Reaction Spontaneity

Match each physical or chemical process on the left with its corresponding entropy change (ΔS\Delta S) characteristic on the right.

  • Dissolution of solid sodium chloride in water: NaCl(s)→Na(aq)++Cl(aq)−\text{NaCl}_{(s)} \rightarrow \text{Na}^+_{(aq)} + \text{Cl}^-_{(aq)}Positive entropy change (ΔS>0\Delta S > 0) due to the breakdown of a rigid crystal lattice into free mobile hydrated ions.
  • Condensation of water vapor into liquid: H2O(g)→H2O(l)\text{H}_2\text{O}_{(g)} \rightarrow \text{H}_2\text{O}_{(l)}Negative entropy change (ΔS<0\Delta S < 0) due to transition from a highly disordered gaseous state to a more ordered liquid state.
  • Sublimation of solid carbon dioxide: \text{CO}_{2(s)} \rightarrow \text{CO}_{2(g)}$Positive entropy change (ΔS>0\Delta S > 0) due to transition from solid directly into a highly disordered gas phase.
  • Industrial synthesis of ammonia gas: N2(g)+3H2(g)→2NH3(g)\text{N}_{2(g)} + 3\text{H}_{2(g)} \rightarrow 2\text{NH}_{3(g)}Negative entropy change (ΔS<0\Delta S < 0) due to a decrease in the total number of gas moles from 4 moles to 2 moles.

Cevap

Each process is matched based on the change in molecular disorder: dissolving solid NaCl produces mobile hydrated ions (positive entropy change), condensing water vapor transitions gas to liquid (negative entropy change), subliming dry ice transitions solid to gas (positive entropy change), and synthesizing ammonia decreases gaseous moles from 4 to 2 (negative entropy change).
Entropy (ΔS\Delta S) is a measure of randomness or molecular disorder. Phase transitions from solid to aqueous or solid to gas increase disorder (ΔS>0\Delta S > 0). Phase transitions from gas to liquid or reactions that reduce the number of gas moles decrease disorder (ΔS<0\Delta S < 0).

Adım Adım Çözüm

1
Analyze state changes and particle freedom for physical processes.
Solid to aqueous ions increases disorder (ΔS>0\Delta S > 0). Gas to liquid decreases disorder (ΔS<0\Delta S < 0). Solid to gas increases disorder (ΔS>0\Delta S > 0).
Gases have the highest entropy, followed by aqueous solutions, liquids, and solids.
2
Analyze gas mole stoichiometry for chemical reactions involving gases.
For N2(g)+3H2(g)→2NH3(g)\text{N}_{2(g)} + 3\text{H}_{2(g)} \rightarrow 2\text{NH}_{3(g)}, reactant gas moles = 1+3=41 + 3 = 4, product gas moles = 22. Since gas moles decrease, ΔS<0\Delta S < 0.
A decrease in the number of gaseous particles decreases the available microstates of the system.

Anahtar Kavram

Predicting the sign of entropy change (ΔS\Delta S) from physical state transitions and changes in total moles of gas
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Konular

Entropy, Free Energy and Reaction Spontaneity