Created by siobhan.quirk
over 11 years ago
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Question | Answer |
Enthalpy | the heat content that is stored in a chemical systen |
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 (-ve) |
Endothermic | a reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting is heat being taken in from the surroundings (+ve) |
Enthalpy profile diagram | is a diagram for a reaction to compare the enthalpy of the reactants with the enthalpy of the products |
Activation energy | the minimum energy required to start a reaction by the breaking of bonds |
Standard conditions | a pressure of 100kPa, a stated temperature usually 298K and a concentration of 1.0moldm-3 |
Standard state | physical state of a substance under standard conditions of 100kPa and 298K |
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 |
Standard enthalpy change of formation | the enthalpy change that takes place when one mole of a compounds is formed from its constituent elements in their standard states under standard conditions |
Specific heat capacity | the energy required to raise the temperature of 1g of a substance by 1 degrees |
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 |
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 |
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 |
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 |
Rate of reaction | the change in concentration of a reactant or product in a given time |
Heterogenous catalysis | catalysis of a reaction in which the catalyst has a different physical state from the reactants |
Homogeneous catalysis | catalysis of a reaction in which the catalysts and reactants are in the same physical state |
Boltzmann Distribution | distribution of energies of molecules at a particular temperature |
Dynamic equilibrium | the equilibrium that exists in a closed system when the rate of the forward reaction is euql to the rate of the reerse reaction |
le Chatelier's principle | states that 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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