The standard enthalpy change of reaction ΔrHθ is the enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions, with all reactants and products in their standard states.ΔrHθ always refers to a stated equation and depends on the stoichiometry and balancing numbers of the equation. For example:Ca(s) + ½O2(g) → CaO(s) ΔrHθ = -635.1 kJ mol-12Ca(s) + O2(g) → 2CaO(s) ΔrHθ = -1270.2 kJ mol-1
Enthalpy Change of a Reaction
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Specification: Edexcel Chemistry (8CH0), AS-level, Topic 8: Energetics I. Topic: Enthalpy.
Key terms in this lesson
- stoichiometry
- The numerical relationship between the amounts of reactants and products in a balanced chemical equation.
More in Enthalpy
- Evaluating Sources of Error
- Standard Enthalpy Change of Neutralisation
- Experimental Determination of Standard Enthalpy Change of Neutralisation
- Standard Enthalpy Change of Formation
- Hess's Law
- Hess's Law Example 2
- Hess's Law Example 3
- Hess's Law Example 4
All 21 lessons in Enthalpy · All Edexcel AS-level Chemistry topics