The standard enthalpy change of formation ΔfHθ is the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard statesBy definition, the standard enthalpy change of formation of an element is zero.The definition refers to the reaction in which one mole of the substance is formed.Ca(s) + ½O2 → CaO(s) ΔfHθ = -644.5kJmol-1
Enthalpy Change of Formation
Read the text
Read the text and highlight anything you think is important. When you go on, the text is hidden and you answer from memory.
Specification: OCR Chemistry A (H032), AS-level, 3.2.1 Enthalpy changes. Topic: Enthalpy.
Key terms in this lesson
- Mole
- The amount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12.
- Enthalpy
- A measure of the total energy of a chemical system.
- Enthalpy change
- The heat energy that is transferred between the system and its surroundings during a process carried out at constant pressure.
- Standard conditions
- A pressure of 100 kPa, a temperature of 298 K, and, for solutions, a concentration of 1 moldm-3.
More in Enthalpy
- Endothermic and Exothermic Reactions
- Activation Energy
- Standard Enthalpy Changes and Standard Conditions
- Enthalpy Change of Reaction
- Enthalpy Change of Combustion
- Enthalpy Change of Neutralisation
- Measuring the Enthalpy Change of Combustion
- Accuracy of Experimental Value
All 19 lessons in Enthalpy · All OCR AS-level Chemistry topics