Use data in Table 4H.1 or Appendix 2A to calculate the standard entropy change for each of the following reactions at 25°C. For each reaction, interpret the sign and magnitude of the reaction entropy.

Table 4H.1

(a) The preparation of manganese metal in the thermite reaction: 4 Al(s) + 3 MnO₂(s) → 3 Mn(s) + 2 Al₂O₃(s).

(b) A reaction used to power rockets: 7 H₂O₂(l) + N₂H₄(l) → 2 HNO₃(aq) + 8 H₂O(l). 

(c) The purification of silicon: SiO₂(s) + 2 C(s) → Si(s) + 2 CO(g). 

(d) The preparation of nitric oxide:

Transcribed Image Text:

2A THERMODYNAMIC DATA AT 25 C Inorganic Substances Substance Aluminum Al(s) Al+ (aq) AI(OH)3(s) AlO3(s) AICI;(s) AlBr,(s) Antimony Sb(s) SbH3(g) SbCl3(g) SbCls (g) Arsenic As(s), gray AsO (aq) A$2S3(S) Barium Ba(s) Ba+ (aq) BaO(s) BaCO3(s) BaCO3(aq) Molar mass, M/(g-mol-) 26.98 26.98 78.00 101.96 133.33 266.68 121.76 124.78 228.11 299.01 74.92 138.92 246.05 137.33 137.33 153.33 197.34 197.34 Enthalpy of formation, AH/(kJ-mol-) 0 -524.7 -1276 -1675.7 -704.2 -527.2 0 +145.11 -313.8 -394.34 0 -888.14 - 169.0 0 -537.64 -553.5 -1216.3 - 1214.78 Gibbs free energy of formation, AG/(kJ.mol-) 0 -481.2 -1582.35 -628.8 0 +147.75 -301.2 -334.29 0 -648.41 -168.6 0 -560.77 -525.1 -1137.6 -1088.59 Molar heat capacity, Cr.m/(J.K-mol). 24.35 79.04 91.84 100.6 25.23 41.05 76.69 121.13 24.64 116.3 28.07 47.78 85.35 Molar entropy,* Sm/(J-K mol) 28.33 -321.7 - 50.92 110.67 180.2 45.69 232.78 337.80 401.94 35.1 - 162.8 163.6 62.8 +9.6 70.42 112.1 -47.3