Chemistry

Problem

For the decomposition reaction

2\,\text{NH}_3(g)\rightarrow\text{N}_2(g)+3\,\text{H}_2(g)

, which statement most accurately predicts the sign of

\Delta H^{\circ}

and the reason for that sign? a)

\Delta H^{\circ}

is negative because the reaction produces more moles of gas, so the increasing disorder releases heat. b)

\Delta H^{\circ}

is negative because forming the three H–H bonds releases more energy than is required to break the N–H bonds (the N≡N bond contribution is ignored). c)

\Delta H^{\circ}

is positive because more energy is required to break the six N–H bonds in ammonia than is released when the N≡N and H–H bonds are formed. d)

\Delta H^{\circ}

is positive because breaking bonds always requires energy whereas forming bonds releases very little energy.

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