Enthalpy Flashcards
Enthalpy
Measure of the heat energy in a chemical system
Enthalpy change
Products - reactants
-ve = Exothermic
+ve = endothermic
Standard Enthalpy change of reaction
Enthalpy change that accompanies a reaction in the molar quantities shown in a chemical equation under standard conditions
Standard Enthalpy change of formation
The Enthalpy change that takes place when one mole of compound is formed from its elements under standard conditions
Standard Enthalpy of combustion
The Enthalpy change that takes place when one mole of substance completely reacts with oxygen under standard conditions
Standard Enthalpy change of neutralisation
Enthalpy change that accompanies the reaction of an acid by a base to form 1 mol of H2O under standard conditions
Calculating energy change
Q=mass x specific heat capacity x change in temp
Accuracy of Enthalpy chance of combustion
Heat loss of surroundings
Incomplete combustion of methanol
Evaporation of methanol from wick
Non standard conditions
Average bond Enthalpy
Energy required to break one mol of a specified type of bond in a gaseous molecule
Always endothermic
Limitation of using bond Enthalpy es
Can vary depending on the chemical environment of the bond
Bond making
Exothermic - Enthalpy is negative
Calculating Enthalpy change from bond Enthalpy es
Bond Enthalpies of reactant - bond enthalpies of products
Hess law
Enthalpy changes to be determined indirectly
Use different Enthalpy values etc
