Use Hess’ Law to determine the overall enthalpy change of each of the following (underlined) processes.

Question

Use Hess’ Law to determine the overall enthalpy change of each of the following (underlined) processes.

CS2(l)+3O2(g) --> CO2(g)+2SO2(g) H = ??? kj

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C(s)+O2(g) --> CO(g) H = -393.5 kj/mol

S(s)+O2(g) --> SO(g) H = -296.8 kj/mol

C(s)+2S(s) --> CS(l) H = +87.9 kj/mol

Answer 1

CS₂(l) + 3O₂(g) --> CO₂(g) + 2SO₂(g) TARGET EQUATION

Given:

(1) C(s) + O₂(g) --> CO₂(g) H = -393.5 kj/mol (note: you must have copied this incorrectly)

(2) S(s) + O₂(g) --> SO₂(g) H = -296.8 kj/mol (note: you must have copied this incorrectly)

(3) C(s) + 2S(s) --> CS₂(l) H = +87.9 kj/mol (note: you must have copied this incorrectly)

Procedure:

reverse (3): CS2(l) --> C(s) + 2S(s) H = -87.9 kj

copy(2) x 2: 2S(s) + 2O₂(g) --> 2SO₂(g) -593.6 kj

copy (1) : C(s) + O₂(g) --> CO₂(g) -393.5 kj

Add them to get:

CS₂(l) + 3O₂(g) --> 2SO₂(g) + CO₂ TARGET EQUATION ∆H = -1075 kJ