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Description
Flashcards by abenabiney, updated more than 1 year ago
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Created by abenabiney
almost 10 years ago
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| Question | Answer |
| Enthalpy | The heat content that is stored in a chemical system |
| Exothermic | Refers to a reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings |
| Endothermic | Refers to 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 |
| Enthalpy profile diagram | A diagram for a reaction to come the enthalpy of the reactants with the enthalpy of the products |
| Activation energy | Minimum energy required to start a reaction by the breaking of bonds |
| Standard conditions | A pressure of 100kPa (1 atmosphere) and a stated temperature, usually 25°C and a concentration of 1.0 mol dm⁻³ |
| 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 |
| 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 | Of a compound is when one mole of a compound is formed from its constituent elements inn their standard states under standard conditions |
| Specific heat capacity | Is the energy required to raise the temperature of 1g of a substance by 1°C |
| 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 |
| 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 | States that, 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 a product in a given time |
| 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 |
| Homogeneous catalysts | 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 |
| Boltzmann distribution | The distribution of energies of molecules at a particular temperature, often shown as a graph |
| le Chatelier's principle | States that when a system in dynamic equilibrium is subjected to change, the position of equilibrium will shift to minimise the change |
| 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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