Question

Use the following information to calculate the heat of formation of propane C3H8.
3 C (S-Graphite) + 4 H2 (g) —› C3H8 (g)

1. C (S-Graphite) + O2 (g) —› CO2 (g) ΔH = - 393.5 kJ

2. H2 (g) + ½ O2 (g) —› H2O (l) ΔH = - 285.8 kJ

3. C3H4 (g) + 4 O2 (g) —› 3 CO2 (g) + 2 H2O (l) ΔH = - 1937 kJ

4. C3H6 (g) + 9/2 O2 (g) —› 3 CO2 (g) + 3 H2O (g) ΔH = - 2007 kJ

5. C3H8 (g) + 5 O2 (g) —› CO2 (g) + 4 H2O (l) ΔH = - 2219.1 kJ

Answer 1

1. C (S-Graphite) + O2 (g) —› CO2 (g) ΔH = - 393.5 kJ --------> 1

2. H2 (g) + ½ O2 (g) —› H2O (l) ΔH = - 285.8 kJ --------------> 2

3. C3H4 (g) + 4 O2 (g) —› 3 CO2 (g) + 2 H2O (l) ΔH = - 1937 kJ --------------> 3

4. C3H6 (g) + 9/2 O2 (g) —› 3 CO2 (g) + 3 H2O (g) ΔH = - 2007 kJ -------------> 4

5. C3H8 (g) + 5 O2 (g) —› CO2 (g) + 4 H2O (l) ΔH = - 2219.1 kJ -------------> 5

equation 1 multifly with 3 and equation 2 multifly with 4

3C (S-Graphite) + 3O2 (g) —› 3CO2 (g)    ΔH = - 1180.5 kJ --------> 1

4 H2 (g) + 2 O2 (g) ---------------> 4H2O (l)           ΔH = - 1143.2kJ --------------> 2

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3C( S-Graphite) + 4H2(g) + 5O2(g) ----------> 3CO2(g) + 4H2O(l)    ΔH = -2323.69KJ

C3H8 (g) + 5 O2 (g) ----------------->3CO2 (g) + 4 H2O (l)                   ΔH = - 2219.1 kJ   ---------> 5 subtract

(-)            (-)                             (-)               (-)                                        (+)

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3 C (S-Graphite) + 4 H2 (g)-----------------------------> C3H8 (g)                     ΔH = -104.59KJ