CHEM1011 Week 9 Questions And Answers

Standard enthalpy of formation correct answer: enthalpy change when it is made from the stable form of its elements at standard condition combustion enthalpy correct answer: exothermic, so always negative atomisation enthalpy correct answer: endothermic, so always positive ∆H(rxn)= correct answer: ∑∆Hºf(products) - ∑∆Hºf(reactants) standard enthalpy of formation correct answer: change of enthalpy during the formation of one mole of the substance from its constituent elements, with all substances in their standard states Hess' Law correct answer: The heat of any formation ΔHºf for a specific reaction is equal to the sum of the heats of reaction, + enthalpy change accompanying a chemical change is independent of the route by which the bond enthalpy correct answer: the amount of energy required to break one mole of the stated bond calculate ∆H using average bond enthalpies correct answer: energy added to break bonds (this should be positive)+ energy released to make product bonds (this should be negative) types of fuels correct answer: solid, liquid, gas gas as a fuel correct answer: lower densities, hard to transport solids as a fuel correct answer: high densities, but cant be used in internal combustion engines liquids as a fuel correct answer: high density, can be used in engines