enthalpy change q

solved this using ∆rH = ∆H products - ∆H reactants but the solutions give a diff ans, was confused, am I wrong or are the solutions wrong?
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iTeachChem Helper
@Dexter
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Comrade Rock Astley
Let’s say there is x amount of energy when all bonds are broken If H2 and Br2 are formed, then bond energy is released So enthalpy of system becomes x-435 -192 Similarly, when 2HBr is formed we get x- 2(BE) Now try using enthalpy of products - reactants
Gravy Bones
Gravy BonesOP10mo ago
used it yea, got C as the ans but the key gave D basically I added up the ∆H of the reactants and used ∆rH = 2(∆HBr) - (∆H H2 + ∆H Br2) am I wrong?
Gravy Bones
Gravy BonesOP10mo ago
it's just the solutions gave this ans it confused me somewhat
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Propellane
Propellane10mo ago
Kinda because the enthalpy values they've given are specifically mentioned as Bond energies (bond enthalpies). You have calculated it by taking it as "enthalpy of reaction". Difference is that the Bond enthalpy of a reaction: (BE) = Sum of BE(reactants) - Sum of BE (products) The key point is that they're talking about bond enthalpies, a special case of enthalpy of reaction.
Gravy Bones
Gravy BonesOP10mo ago
got it thanks!!! +solved @Propellane
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