Topic 4 0.0 / 5 ? ChemistryEnergeticsASAQA Created by: Jemma1494Created on: 01-06-21 18:34 Hess law Enthalpy change is the same no matter what route is taken 1 of 10 Bond enthalpy Bond enthalpy = reactants - products 2 of 10 Standard enthalpy of formation Enthalpy change for one mole of a molecule to be made from its elements Elements = 0 Up arrows in hess cycles 3 of 10 Standard enthalpy of combustion Enthalpy change for one mole of a molecule to be completely burned in oxygen Oxygen = 0 Down arrows in hess cycles 4 of 10 Breaking bonds Requires energy 5 of 10 Making bonds Releases energy 6 of 10 Exothermic Negative enthalpy change Releases heat Making bonds releases more energy than breaking 7 of 10 Endothermic Positive enthalpy change Requires heat Breaking bonds requires more energy than making 8 of 10 Enthalpy change equation Q = mc ΔT ΔH = q/moles 9 of 10 Natural states Bromine and mercury = (l) Group 0,N,O,F,Cl,H = (g) Other = (s) 10 of 10
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