Question

Thermodynamics

-Predict whether the following reaction will result in either a positive, negative, or zero ΔS_rxn­.The deposition of molecular iodine: I₂ (g) → I₂ (s)

-Predict whether the following reaction will result in either a positive, negative, or zero ΔS_rxn­.The dissolution of lithium chloride: LiCl (s) → Li⁺ (aq) + Cl^– (s)

-Predict whether the following reaction will result in either a positive, negative, or zero ΔS_rxn­.The dimerization of nitrogen dioxide: 2 NO₂ (g) → N₂O₄ (g)

-Predict whether the following reaction will result in either a positive, negative, or zero ΔS_rxn­.The combustion of methane: CH₄ (g) + 2 O₂ (g) → CO₂ (g) + 2 H₂O (g)

Answer 1

(a) The entropy decreases (∆S<0) as the substance transform from a gas to solid.

(b) The entropy increases ∆S>0 when an ionic compound dissociates in to its ions as the free ions are continually moving throughout as they are attracted and repulsed by the polar ends of the water molecules. The solution is more disordered than a pure liquid.

(c) In case of dimerization of Niyrogen dioxide there is increase in entropy ∆S>0.

(d) Entropy change for combustion of methane is negative so ∆S<0