Uploaded April 2026 | Updated September 2026, 3 weeks ago

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Enthalpy (ΔH) Numericals Made Easy 🔥 | Thermochemistry Class 11 | NEET/JEE

Most students lose marks here — but the rules are simple:

Rule 1: Multiply/Divide reaction → ΔrH° also changes
Rule 2: Reverse reaction → sign of ΔrH° flips

Watch this:
Fe₂O₃ + 3H₂ → 2Fe + 3H₂O → ΔrH° = −33.3 kJ/mol
½ reaction → ΔrH° = −16.6 kJ/mol

Conclusion: Enthalpy is an extensive property

Exam Trick:
Change coefficients = Change ΔH
Reverse reaction = Change Sign

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