Chemistry Definitions: Module 3

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  • Created by: ABusby1
  • Created on: 11-01-16 11:48
Enthalpy, H
The heat energy stored in a chemical system
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Exothermic
When the enthalpy is smaller at then end of a reaction than at the beginning. Resulting in heat loss. Deltah -ve.
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Endothermic
When the enthalpy is greater at then end of a reaction than at the beginning. Resulting in heat being taken in. Deltah +ve.
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Activation energy
Minimum energy required to start a reaction by the breaking of bonds.
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Enthalpy profile diagram
Shows the enthalpy of the reactants and products along with the activation energy and enthalpy change.
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Standard conditions
Pressure of 100kpa and Temperature of 298K in solution concentration of 1M.
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Standard state
The state we find a substance in under standard conditions.
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Standard enthalpy change of reaction
Is the enthalpy change that accompanies the moles given in a balanced equation are reacted under standard conditions and in standard states
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Standard enthalpy change of combustion
Is the enthalpy change when one mol of reactant is burned completely in oxygen under standard conditions
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Standard enthalpy change of formation
Is the enthalpy change when 1 mol of product is formed from its constituent elements in standard states under standard conditions.
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Specific heat capacity, C
Energy required to heat 1g of substance by 1K.
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Bond enthalpy
Is the enthalpy change when 1 mol of given bonds is broken by homolytic fission in a gaseous state.
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Hess' Law
"if a reaction can take place by more than 1 route and the initial and final conditions are the same, the total enthalpy change is the same for each route."
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Rate of reaction
The change in concentration of a reactant or product in a given time.
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Catalyst
A species than lowers the activation energy of a reaction by providing an alternate route but is not used itself.
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Boltzmann distribution
Is the distribution of energies of molecules within a sample at a given temperature.
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Dynamic equilibriu m
An equilibrium in a closed system where the rate of forward reaction equals that of the reverse reaction leaving constant concentrations of products and reactants.
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Le chatelier's principle
When a change is imposed on a system in dynamic equilibrium the position of the equilibrium will change to minimise the change.
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Other cards in this set

Card 2

Front

When the enthalpy is smaller at then end of a reaction than at the beginning. Resulting in heat loss. Deltah -ve.

Back

Exothermic

Card 3

Front

When the enthalpy is greater at then end of a reaction than at the beginning. Resulting in heat being taken in. Deltah +ve.

Back

Preview of the back of card 3

Card 4

Front

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

Back

Preview of the back of card 4

Card 5

Front

Shows the enthalpy of the reactants and products along with the activation energy and enthalpy change.

Back

Preview of the back of card 5
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