For the decomposition 2 NH₃(g) → N₂(g) + 3 H₂(g)

CHEMISTRY · Single correct · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

For the decomposition 2 NH₃(g) → N₂(g) + 3 H₂(g), which statement correctly compares the entropy change at 800 K to the entropy change at 298 K? (a)

\Delta S^{\circ}

is positive at

298\,\text{K}

but approximately zero at

800\,\text{K}

because entropy is inversely proportional to temperature. (b)

\Delta S^{\circ}

is positive at both temperatures and has a larger magnitude at

800\,\text{K}

because the entropy of gases increases with temperature. (c)

\Delta S^{\circ}

is positive at both temperatures and has the same magnitude because temperature affects the entropies of reactants and products proportionally. (d)

\Delta S^{\circ}

is positive at

298\,\text{K}

but becomes less positive at

800\,\text{K}

because the increased kinetic energy offsets the disorder created by the additional gas molecules.