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प्रश्न
Given
\[\ce{N_{2(g)} + 3H_{2(g)} -> 2NH_{3(g)}}\]; ΔrHθ = –92.4 kJ mol–1
What is the standard enthalpy of formation of NH3 gas?
उत्तर
Standard enthalpy of formation of a compound is the change in enthalpy that takes place during the formation of 1 mole of a substance in its standard form from its constituent elements in their standard state.
Re-writing the given equation for 1 mole of NH3(g),
\[\ce{1/2 N_{2(g)} + 3/2 H_{2(g)} -> NH_{3(g)}}\]
Standard enthalpy of formation of NH3(g)
= ½ ΔrHθ
= ½ (- 92.4 kJ mol-1)
= - 46.2 kJ mol-1
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