Enthalpy is an extensive property- In general- if enthalpy of an overall reaction A - B along one route is - r H and - r H and - r H 1- - r H 2- - r H 3- represent enthalpies of intermediate reactions leading to product B- What will be the relation between - r Hoverall reaction and - r H 1- - r H 2- etc for intermediate reactions-

In general, if enthalpy of an overall reaction A → B along one route is Δ_r H and Δ_r H and Δ_r H_1, Δ_r H_2, Δ_r H_3 ⋯ representing enthalpies of reaction lead ...

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Standard XII

Chemistry

Hess' Law

Enthalpy is a...

Question

Enthalpy is an extensive property. In general, if enthalpy of an overall reaction A $\to$ B along one route is $Δ_{r} H$ and $Δ_{r} H a n d Δ_{r} H_{1}, Δ_{r} H_{2}, Δ_{r} H_{3} \dots$ represent enthalpies of intermediate reactions leading to product B. What will be the relation between $Δ_{r} H$ overall reaction and $Δ_{r} H_{1}, Δ_{r} H_{2} \dots$ etc for intermediate reactions.

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Solution

In general, if enthalpy of an overall reaction A $\to$ B along one route is $Δ_{r} H$ and $Δ_{r} H and Δ_{r} H_{1}, Δ_{r} H_{2}, Δ_{r} H_{3} \dots$ representing enthalpies of reaction leading to same product B along another route, then we have
$Δ_{r} H = Δ_{r} H_{1} + Δ_{r} H_{2} + Δ_{r} H_{3} + \dots$
Note For a general reaction Hess's law of constant heat summation can be represented as

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