The equation for the reaction between ammonia and oxygen is shown. 4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g) . Calculate the entropy change of the reaction, using data from the table below.
GAS So / J K-1 mol-1 NH3(g) 193 O2(g) 205 NO(g) 211 H2O(g) 189
To calculate the entropy change, use Delta S = sum of products - sum of reactants, in their corresponding stoichometry. Remember to check the units are all the same, which they are in this case.
Therefore, the answer will be:
= [ (4 x 211) + (6 x 189) ] - [ (4 x 193) + (5 x 205) ] = ( 1978 – 1797) 181 (J K-1 mol-1 ), remembering units.
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