The heat content that is stored in a chemical system (H)
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Exothermic
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (delta H = -ve)
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Endothermic
A 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 (delta H = +ve)
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Enthalpy Profile Diagram
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
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Activation Energy
The minimum energy required to start a reaction by breaking bonds
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Standard State
The physical state of a substance under the standard conditions of 100 kPa (1 atmosphere) and 298K (25 degrees C)
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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
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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 states
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Standard Enthalpy Change of Formation
The 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
The energy required to raise the temperature of 1g of a substance by 1 degree C
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Bond Enthalpy
The 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
The 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 that 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
A diagram showing alternative routes between reactants and products which allows the indirect determination of an enthalpy change from other known enthalpy changes using Hess' Law
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Rate of Reaction
The change in concentration of a reactant or a product in a given time
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Heterogeneous Catalysis
Catalysis of a reaction in which the catalyst has a different physical state from the reactants; frequently, reactants are gases whilst the catalyst is a solid
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Homogeneous Catalysis
Catalysis of a reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state
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Dynamic Equilibrium
The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction
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le Chatelier's Principle
When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the change
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Other cards in this set
Card 2
Front
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (delta H = -ve)
Back
Exothermic
Card 3
Front
A 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 (delta H = +ve)
Back
Card 4
Front
A diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products
Back
Card 5
Front
The minimum energy required to start a reaction by breaking bonds
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