For the reaction at 298 K

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

Problem

For the reaction

3\,\text{C}(s,\text{graphite}) + 4\,\text{H}_2(g) \rightarrow \text{C}_3\text{H}_8(g)

at 298 K, the measured standard entropy change is

\Delta S^{\circ} = -94.6\,\text{J K}^{-1}

. The absolute molar entropies of

\text{H}_2(g)

and

\text{C}_3\text{H}_8(g)

are 130.6

\text{J K}^{-1}\,\text{mol}^{-1}

and 269.9

\text{J K}^{-1}\,\text{mol}^{-1}

, respectively. Which of the following algebraic expressions correctly gives the standard molar entropy

S^{\circ}(\text{C})

for graphite when evaluated? (a)

\dfrac{4(130.6)-269.9-(-94.6)}{3}

(b)

\dfrac{269.9-4(130.6)-94.6}{3}

(c)

\dfrac{269.9-4(130.6)-(-94.6)}{3}

(d)

269.9-4(130.6)-(-94.6)