1930752
AS Chemistry - Enthalpy Changes
- Exothermic and Endothermic
- Endothermic
- The absorption of energy to the surroundings
- Delta H is positive
- Themal Decomposition
- Photosynthesis
- The absorption of energy to the surroundings
- Exothermic
- The release of energy to the surroundings
- Delta H is negative
- Combustion
- Respiration
- The release of energy to the surroundings
- Endothermic
- Types of enthalpy change
- Standard Enthalpy Change of Reaction
- The enthalpy change that accompanies a reaction in the
molar quantities expressed in a chemical equation under
standard conditions, all reactants and products being in
their standard states
- The enthalpy change that accompanies a reaction in the
molar quantities expressed in a chemical equation under
standard conditions, all reactants and products being in
their standard states
- Standard Enthalpy Change of Combustion
- The enthalpy change that takes place when one mole of a
substance reacts completely with oxygen under standard
conditions, all reactants and products being in their standard state
- The enthalpy change that takes place when one mole of a
substance reacts completely with oxygen under standard
conditions, all reactants and products being in their standard state
- Standard Enthalpy Change of Formation
- The enthalpy change that takes place when one mole of a
compound is formed from its constituent elements under
standard conditions, all reactants and products being in
their standard states
- The enthalpy change that takes place when one mole of a
compound is formed from its constituent elements under
standard conditions, all reactants and products being in
their standard states
- Standard Enthalpy Change of Reaction
- Determining the enthalpy
change
- q= m x c x delta t
- q - enthalpy change (Joules)
- m - mass of
surroundings
involved in heat
exchange
- c - specific heat capacity
- delta t - temperature
change of
surroundings
- q= m x c x delta t
- Bond Enthalpies
- the enthalpy change that takes place
when breaking by homolytic fission 1
mole of a given bond in the molecules of
a gaseous species
- Bond breaking - ENDOTHERMIC - energy is
needed to break bonds
- Bond making - EXOTHERMIC - energy is released
when making bonds
- Using average bond enthalpies
to determine enthalpy changes
- Delta H = the sum of the bond enthalpies of bonds broken -- the sum of the bond enthalpies of bonds made
- Delta H = the sum of the bond enthalpies of bonds broken -- the sum of the bond enthalpies of bonds made
- the enthalpy change that takes place
when breaking by homolytic fission 1
mole of a given bond in the molecules of
a gaseous species
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