Question
Explain standard heat of formation with example.
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Answer
Standard enthalpy of formation $\left(\Delta_f H^{\ominus}\right)$ : The standard enthalpy change that occurs when one mole of compound is formed from its constituent elements, which are taken in their most stable forms, is called standard enthalpy of formation.
Here subscript ' $f$ ' indicates that one mole of concerned compound has been obtained from its elements which are in their most stablest form.
Example : $C _{\text {(s)graphite }}+2 H _2(g) \rightarrow CH _4(g)$
$\Delta_{ f } H ^{\ominus}=-74.81 kJ mol ^{-1}$
Here subscript ' $f$ ' indicates that one mole of concerned compound has been obtained from its elements which are in their most stablest form.
Example : $C _{\text {(s)graphite }}+2 H _2(g) \rightarrow CH _4(g)$
$\Delta_{ f } H ^{\ominus}=-74.81 kJ mol ^{-1}$
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