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Thermodynamics question

2004 · Q106
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Thermodynamics question

2004 · Q106

NEETChemistryThermodynamicsMCQ+4 / −1
If the bond energies of H −-− H, Br −-− Br, and H −-− Br are 433, 192 and 364 kJ mol−-−1 respectively, the Δ\DeltaΔHo for the reaction

H2(g) + Br2(g) →\to→ 2HBr(g) is
  1. A
    −-− 261 kJ
  2. B
    +103 kJ
  3. C
    +261 kJ
  4. D
    −-−103 kJ
View written solutionFree

Correct answer: D

H2(g) + Br2(g) →\to→ 2HBr(g),   Δ\Delta ΔHof = ?

Δ\Delta ΔHof = Σ\Sigma Σ(B.E.)reactants – Σ\Sigma Σ(B.E.)products

= (B.E.)H–H + (B.E.)Br–Br –2(B.E)H-Br

= [433 + 192] – 2(364) kJ mol–1

= (625 – 728) kJ mol–1 = –103 kJ mol–1

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