Same chapter3 marksDifficulty: Medium
Calculate the enthalpy change of a reaction whose bond enthalpies give 1,200 kJ absorbed to break bonds and 1,500 kJ released to form them.
Chemical Thermodynamics
3 marksDifficulty: Medium
State Hess's law and give one use of it.
Original Khojo Papers practice question — not from a past board paper.
Answer
Hess's law states that the total enthalpy change of a reaction is the same whether it takes place in one step or in several, provided the initial and final states are the same. It is used to calculate enthalpy changes that cannot be measured directly, such as the enthalpy of formation of carbon monoxide.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
It follows from enthalpy being a state function.
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