Formation of ammonia is shown by the reaction, N2(g)+3H2(g)→2NH3(g);△rH0 = −91.8kJmol−1. What will be the enthalpy of reaction for the decomposition of NH3 according to the reaction? 2NH3(g)→N2(g)+3H2(g),△rH0 = ?
A
−91.8kJmol−1
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B
+91.8kJmol−1
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C
−45.9kJmol−1
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D
+45.9kJmol−1
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Solution
The correct option is B+91.8kJmol−1 The given reaction is:-
N2(g)+3H2(g)→2NH3(g);△rH0=−91.8KJ/mol
Nor, for the reaction
2NH3(g)→N2(g)+3H2(g)
△rH0=−(−91.8)=+91.8KJ/mol
(since this reaction is reverse reaction of the above given reaction so the sign of △H will get reversed).