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Description
Flashcards by siobhan.quirk, updated more than 1 year ago
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Created by siobhan.quirk
almost 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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