The standard enthalpy change of combustion ΔcHθ is the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions with all the reactants and products in their standard states.The reaction with oxygen produces oxides and is always exothermic. For the combustion of methane:CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ΔcHθ = - 890 kJmol-1
Enthalpy Change of Combustion
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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.
- Exothermic
- Describes a process in which heat energy is transferred from the system to the surroundings, so the enthalpy change is negative.
- Standard conditions
- A pressure of 100 kPa, a temperature of 298 K, and, for solutions, a concentration of 1 moldm-3.
More in Enthalpy
- Activation Energy
- Standard Enthalpy Changes and Standard Conditions
- Enthalpy Change of Reaction
- Enthalpy Change of Formation
- Enthalpy Change of Neutralisation
- Measuring the Enthalpy Change of Combustion
- Accuracy of Experimental Value
- Determining the Enthalpy Change of a Reaction
All 19 lessons in Enthalpy · All OCR AS-level Chemistry topics