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Starter. What are standard conditions? Classify as endothermic or exothermic. Combustion of methane Respiration Photosynthesis NaOH + HCl. Determination of Enthalpy Changes. L.O.:

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  1. Starter • What are standard conditions? • Classify as endothermic or exothermic. • Combustion of methane • Respiration • Photosynthesis • NaOH + HCl

  2. Determination of Enthalpy Changes L.O.: Define and use the terms: standard conditions; enthalpy change of reaction; enthalpy change of formation; and enthalpy change of combustion.

  3. Standard enthalpy change of formation , ∆Hѳf, of a compound is the enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard state under standard conditions. • Example(s): C(s,graphite) + O2(g) ———> CO2(g) H2(g) + ½O2(g) ———> H2O(l) 2C(s,graphite) + ½O2(g) + 3H2(g) ——>C2H5OH(l)

  4. Task: Write equations for standard enthalpy change of formation for • C3H8 • MgO • Ethanol • Al2O3

  5. Standard enthalpy change of combustion, ∆Hѳc, is 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 state. Example(s): C(s, graphite) + O2(g) ———> CO2(g) H2(g) + ½O2(g) ———> H2O(l) C2H5OH(l) + 3O2(g) ———> 2CO2(g) + 3H2O(l)

  6. Task: Write equations for the change that occurs during the enthalpy change of formation of: • CH4 • MgO • Ethanol • Al2O3

  7. L.O.: • Calculate enthalpy changes directly from appropriate experimental results, including the use of the relationship: energy change = mcΔT.

  8. An excess of magnesium is added to to 100cm3 of 2.00 mol dm-3 CuSO4(aq). The temperature increases from 20.0 to 65.0 oC. Find the enthalpy change for this reaction (c= 4.18 Jg-1k-1)

  9. Allan’s 3.3

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