Use the table below to answer the questions that follow. Thermodynamic Quantitie

ID: 968380 • Letter: U

Question

Use the table below to answer the questions that follow.

Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)

Substance H°f (kJ/mol) G°f (kJ/mol) S (J/K-mol)

Carbon

C (s, diamond) 1.88 2.84 2.43

C (s, graphite) 0 0 5.69

C2H2 (g) 226.7 209.2 200.8

C2H4 (g) 52.30 68.11 219.4

C2H6 (g) -84.68 -32.89 229.5

CO (g) -110.5 -137.2 197.9

CO2 (g) -393.5 -394.4 213.6

Hydrogen

H2( g) 0 0 130.58

Oxygen

O2 (g) 0 0 205.0

H2O (l) -285.83 -237.13 69.91

The value of S° for the combustion of ethane to carbon dioxide and water vapor,

2C2H6 (g) + 7 O2 (g) 4CO2 (g) + 6H2O (g)

is __________ J/K mol. The value of H for this reaction is__________ kJ/mol.

2C2H6 (g) + 7 O2 (g) 4CO2 (g) + 6H2O (l)

S° for reaction = 2* entropy of C2H8(g) + 7 * entropy of O2(g) - 4* entropy of CO2(g) - 6 * entropy of H2O (g)

= 2* 229.5 + 7 * 205.0 - 4* 213.6 - 6* 69.91 = 620.14J/K -mol

H for this reaction = 2* H°f (kJ/mol)(C2H6(g) + 7 * H°f (kJ/mol)(O2(g)) - 4 * H°f (kJ/mol)(CO2(g) - - 6* H°f (kJ/mol) (H2O)(g)

= 2(-84.68) + 7(0) -4(-393.5) -6(-285.83) = 3119.62 kJ /mol

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