In the previous blog post, we have defined the Enthalpy Change of Combustion as well as other enthalpy changes.
For a quick recap, Standard Enthalpy Change of Combustion is defined as:
Energy released when 1 mole of a substance is completely burned in oxygen under standard conditions
e.g. C2H4 (g) + 3 O2 (g) → 2 CO2 (g) + 2 H2O (l) ΔHcθ(C2H4)
Experimental Determination of Enthalpy Change of Reaction
The First Law of Thermodynamics states that energy cannot be created or destroyed; it can only be converted from one form into another. Based on this law, we can determine the enthalpy change of a reaction.
- System is defined as the reaction (part of the universe which is being studied).
- Surrounding is defined as the environment of the reaction (rest of the universe that is not part of the system).
The enthalpy change of a reaction is heat (at constant pressure). The heat given out (or taken in) by a reaction is transferred to the surrounding). The surrounding is often some water, a solution containing the reactants or products, or even the air.