This is the region which is being investigated. (The reactants and the products.)
This is everything that is affected by the chemical reaction. (The rest of the universe.)
- A reaction that gives out heat to the surroundings is EXOTHERMIC
- A reaction that takes in heat from the surroundings is ENDOTHERMIC
Enthalpy Change (∆H)
This is the heat energy change measured under conditions of constant heat and pressure.
If trying to work out the ∆H from a graph; ∆H = H2 – H1
This is a stoichiometric equation which includes the states of the reactants and products, and a value for the enthalpy change of the forward reaction.
This is a method of measuring the enthalpy change of a reaction by considering temperature changes in the immediate surroundings of the chemical reaction.
This is an insulated vessel which is used for measuring the amount of energy released/ absorbed during a chemical/ physical change.
Amount of heat transferred = Mass of the substance × Specific Heat Capacity × Temperature Change
q = mc∆T
Enthalpy Change = ± (Endothermic/Exothermic) Amount of heat transferred ÷ Amount of substance
∆H = ± q / n
Calculate the heat capacity of the Calorimeter;
c = n∆H / ∆T
q = c∆T
The overall enthalpy change is independent upon the route taken.
Enthalpy of Formation
The enthalpy change when one mole of a compound is formed under its constituent elements under standard conditions, all reactants and products in their standard states.
∆Hr = Σ∆Hθf (Products) - Σ∆Hθf (Reactants)
Enthalpy of Combustion
The enthalpy change when one mole of a compound is completely burned in oxygen under standard conditions, all reactants and products in their standard states.
∆Hr = Σ∆Hθc (Reactants) - Σ∆Hθc (Products)
Mean Bond Enthalpy
This is the amount of energy needed to break 1 particular covalent bond averaged over several compounds.
∆Hr = ΣE(Bonds Broken) - ΣE(Bonds Formed)
This is the end of the topic!
Drafted by Cherry (Chemistry)