Energetics
Enthalpy and Hess’s Law
Enthalpy (H) is a measure of the heat content of a substance
Changes in enthalpy can be measured
ΔH = change in heat content at constant pressure
ΔH = enthalpy change measured under standard conditions
Standard conditions = 100 kPa & stated temperature {normally, 298K}
Enthalpy change of formation (ΔHf) =
Enthalpy change when 1 mole of a substance is
made from its constituent elements in their standard
states under standard conditions.
Enthalpy change of combustion (ΔHc) =
Enthalpy change when 1 mole of a substance is burned completely in oxygen under
standard conditions.
Enthalpy change of Neutralisation (ΔHN) =
Enthalpy change when 1 mole of water is formed in a reaction between an acid and
alkali under standard conditions.
,
Enthalpy and Hess’s Law
Enthalpy (H) is a measure of the heat content of a substance
Changes in enthalpy can be measured
ΔH = change in heat content at constant pressure
ΔH = enthalpy change measured under standard conditions
Standard conditions = 100 kPa & stated temperature {normally, 298K}
Enthalpy change of formation (ΔHf) =
Enthalpy change when 1 mole of a substance is
made from its constituent elements in their standard
states under standard conditions.
Enthalpy change of combustion (ΔHc) =
Enthalpy change when 1 mole of a substance is burned completely in oxygen under
standard conditions.
Enthalpy change of Neutralisation (ΔHN) =
Enthalpy change when 1 mole of water is formed in a reaction between an acid and
alkali under standard conditions.
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