Unit 3

Enthalpy
Heat content that is stored in a chemical system
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Exothermic
Reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants,resulting in heat loss to the surroundings.
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Endothermic
Reaction in which the enthalpy of the products is greater than the enthalpy of the reactants,resulting in heat being taken in from the surroundings.
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Enthalpy profile diagram
Diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products.
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Activation energy
Minimum energy required to start a reaction by the breaking of bonds
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Standard conditions
A pressure of 100kPa(1 atmosphere) and a temperature of 298K
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Standard state
Physical state of a substance under the standard conditions
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Standard enthalpy change of combustion
Enthapy 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 states
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Standard enthalpy change of formation
Enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
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Specific heat capacity
Energy required to raise the temperature of 1g of a substance by 1 degree celcius
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Bond enthalpy
Enthalpy change that takes place when breaking by homolytic fission 1 mol of a given bond in the molecules of a gaseous species
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Average bond enthalpy
Average enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species.
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Hess' law
If a reaction can take place by more than one route and the initial and final conditions are the same,the total enthalpy change is the same for each route.
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Enthalpy cycle
Diagram showing alternative routes between reactants andd products which allows the indirect determination of an enthalpy changes using Hess' law.
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Other cards in this set

Card 2

Front

Reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants,resulting in heat loss to the surroundings.

Back

Exothermic

Card 3

Front

Reaction in which the enthalpy of the products is greater than the enthalpy of the reactants,resulting in heat being taken in from the surroundings.

Back

Preview of the back of card 3

Card 4

Front

Diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products.

Back

Preview of the back of card 4

Card 5

Front

Minimum energy required to start a reaction by the breaking of bonds

Back

Preview of the back of card 5
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