We can use the following equation to solve for **ΔS˚**** _{rxn}**:

$\overline{){\mathbf{\u2206}\mathbf{S}\mathbf{\xb0}}_{\mathbf{rxn}\mathbf{}}{\mathbf{=}}{\mathbf{}}{\mathbf{S}\mathbf{\xb0}}_{{\mathbf{prod}}}{\mathbf{-}}{\mathbf{S}\mathbf{\xb0}}_{\mathbf{react}\mathbf{}}}$

Note that we need to *multiply each S˚ by the stoichiometric coefficient* since S˚ is in J/mol • K.

The given reaction is 2H_{2}(g)+O_{2}(g)→2H_{2}O(l)

Given:

S° H_{2}O(g) = 130.6 J/(K•mol)

S° O_{2}(g) = 205.0 J/(K•mol)

S° H_{2}O(l) = 69.90 J/(K•mol)

Calculate the standard entropy change for the reaction 2H_{2}(g)+O_{2}(g)→2H_{2}O(l) using the data from the following table:

Substance | ΔH°_{f} (kJ/mol) | ΔG°_{f} (kJ/mol) | S° [J/(K•mol)] |

H2O(g) | 0.00 | 0.00 | 130.6 |

O2(g) | 0.00 | 0.00 | 205.0 |

H2O(l) | -285.8 | -237.2 | 69.90 |

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