1. What Is the Value of Δssurr for the Following Reactions at 25 ºc and 1 Atm

AP ChemistryName :

Worksheet : Ch. 16 problemsDate :

A. Work with one other partner to practice these problems. Show all work (answers below).

1. What is the value of ΔSsurr for the following reactions at 25 ºC and 1 atm :

a. H2O(l)  H2O(g) ΔH = +44 kJ

b. XeF6(g)  XeF4(s) + F2(g) ΔH = +43 kJ

2. Determine the value of ΔGº for the following reaction from the given values. Determine if the reaction is or is not spontaneous at standard conditions.

N2(g) + 3H2(g)  2NH3(g)

/ Hº (kJ/mol) / Sº (J/K·mol)
N2 / 0 / 192
H2 / 0 / 131
NH3 / -46 / 193

3. At what temperatures will a reaction with a ΔH value of -103.2 kJ and a ΔS value of -245 J/K be spontaneous?

4. Determine the value of ΔGº from the following reaction : S(s) + O2(g)  SO2(g) from the following data :

S(s) + 3/2 O2(g)  SO3(g) ΔGº = -371 kJ

2SO2(g) + O2(g)  2SO3(g) ΔGº = -142 kJ

5. Calculate ΔG at 700.K for the following reaction and determine if it is spontaneous or not :

C(s, graphite) + H2O(g)  CO(g) + H2(g)

Initial pressures : PH2O = .90 atm, PCO = .0020 atm, PH2 = .0020 atm

ΔGºCO = -137 kJ/mol, ΔGºH2O = -229 kJ/mol

6. For the following reaction ΔGº = -537kJ. Calculate K for this reaction and predict the spontaneity of this reaction at 50. ºC.

Cr2O3(s) + 2 Al(s)  Al2O3(s) + 2Cr(s)

7. For the following reaction : C6F6(g)  3 C2F2(g) :

For C6F6(g) : ΔHº = 132.8 kJ/mol, ΔGº = 78.2 kJ/mol

For C2F2(g) : ΔHº = 241.3 kJ/mol, ΔGº = 191.2 kJ/mol

a. Calculate ΔSº at 298 K.

b. Calculate K at 298 K.

Answers : 1a. –150 J/K 1b. –140 J/K 2. –33kJ, spontaneous 3. below 421 K 4. –300. kJ 5. 20. kJ, nonspontaneous, would be spontaneous at higher temperatures and/or lower pressures 6. K = 7.23 x 1086 – “very” spontaneous 7a. S = 321 J/K 7b. K = 1.38 x 10-87