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| Question | Answer |
| Enthalpy | heat content that is stored in a chemical system |
| Exothermic | enthalpy of the products is smaller than the enthalpy of the reactants resulting in heat loss to the surroundings Enthalpy change = -ve |
| Endothermic | enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings Enthalpy change = +ve |
| Activation Energy | minimum energy required to start a reaction by the breaking of bonds |
| Standard State | physical state of a substance under standard conditions |
| Standard enthalpy change of reaction | enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products in their standard states |
| Standard enthalpy change of combustion | 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 | enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard conditions enthalpy of formation of an element = 0kJ/mol |
| Specific heat capacity | energy required to raise the temperature of 1g of a substance by 1degC |
| Bond enthalpy | enthalpy change that takes place when breaking 1 mole of a given bond in the molecule of a gaseous species by homolytic fission |
| Average bond enthalpy | average enthalpy change that takes place when breaking 1 mol of a given type of bond in the molecules of a gaseous species by homolytic fission |
| 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 |
| rate of reaction | change in concentration of a reactant or product in a given time |
| Homogeneous catalyst | catalyst has a different physical state from the reactants |
| Heterogeneous catalyst | catalyst and reactants are in different physical states |
| Boltzmann distribution | distribution of energies of molecules at a particular temperature - usually shown as a graph |
| Dynamic equilibrium | equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction |
| 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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