Enthalpy Change Deffinitions 2.5 / 5 based on 2 ratings ? ChemistryEnthalpyA2/A-levelOCR Created by: charllclarkCreated on: 19-04-16 11:47 An exothermic reaction is A reaction where heat is released from the system signified by a tempreture increase and the product has a lower enthalpy than the reactants 1 of 13 An endothermic reaction is A reaction where heat is gained by the system signified in a tempreture decrease and the products enthalpy is greater than the reactants 2 of 13 Breaking chemical bonds and attractions is Endothermic 3 of 13 Activiation energy is The minimum amount of energy required by the reactants in order to form the products 4 of 13 Standard thermochemical conditions are 100kPa, 298k (25 degrees C) and 1 mol dm-3 concnetration 5 of 13 Enthalpy change of combustion is The exothermic heat change which accompanies the complete combustion of one mole of a substance 6 of 13 Enthalpy change of formation is The heat chnage which accompamies the formation of one mole of a substance from its elements in their normal states 7 of 13 Enthalpy change of neutrilisation is The exothermic heat chnage which accompanies the production of one mole of water when an acid reacts with an alkali 8 of 13 Calorimetry calculations Q= mc(delta T) and (delta H)=Q/n 9 of 13 Give 2 reasons why experimental results of the determination of enthalpy chnage and combustion is very inaccurate incomplete combustion and heat loss surrounding the experiment 10 of 13 Average bond enthalpies are The endothermic heat change to break one mole of covalent bonds in gaseous molecules averaged over a range of molecules with that same bond 11 of 13 equation for calculating bond enthalpies (delta H)= sum of Bonds broken-sum of bonds made 12 of 13 State Hess' law The total enthalpy change from the reactants to products is the same inderpendant of the rout taken 13 of 13
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