Given:
$straight N subscript 2 left parenthesis straight g right parenthesis space plus space 3 straight H subscript 2 left parenthesis straight g right parenthesis space rightwards arrow space space 2 NH subscript 3 left parenthesis straight g right parenthesis semicolon space space space space space space space space space space space space space space space space space space increment subscript straight r straight H to the power of 0 space equals space minus 92.4 space kJ space mol to the power of negative 1 end exponent$
What is the standard enthalpy of formation of NH₃ gas?

Solution

The enthalpy of formation of ammonia is the enthalpy change for the formation of 1 mole of ammonia from its elements.
Given that enthalpy of formation for 2 moles of NH₃ = –92.4 kJ
Therefore, standard enthalpy of formation for

Hence standard enthalpy of formation for NH₃
$straight i. straight e. space space space space increment subscript straight f straight H to the power of 0 ? left parenthesis NH subscript 3 right parenthesis space equals space minus 46.2 space kJ$