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# Thermochemical calcs

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### Thermochemical calcs

1. 1. Thermochemical Calculations
2. 2. CA StandardsStudents know energy is released when a materialcondenses or freezes and is absorbed when a materialevaporates or melts.Students know how to solve problems involving heat flowand temperature changes, using known values of specificheat and latent heat of phase change.
3. 3. Units for Measuring HeatThe Joule is the SI system unit formeasuring heat: 2 1 kg m 1 Joule 1 newton meter 2 sThe calorie is the heat required to raisethe temperature of 1 gram of water by1 Celsius degree 1calorie 4.18 Joules
4. 4. Specific HeatThe amount of heatrequired to raisethe temperature ofone gram ofsubstance by onedegree Celsius. 5 6 5 6 4 7 4 7 3 8 3 8 2 9 2 9 1 11 1 10
5. 5. Calculations Involving Specific Heat Q Q m T cp OR cp m T cp = Specific Heat Q = Heat lost or gained T = Temperature change m = Mass
6. 6. Specific HeatThe amount of heat required to raise the temperatureof one gram of substance by one degree Celsius. Substance Specific Heat (J/g·K) Water (liquid) 4.18 Ethanol (liquid) 2.44 Water (solid) 2.06 Water (vapor) 1.87 Aluminum (solid) 0.897 Carbon (graphite,solid) 0.709 Iron (solid) 0.449 Copper (solid) 0.385 Mercury (liquid) 0.140 Lead (solid) 0.129 Gold (solid) 0.129
7. 7. Latent Heat of Phase ChangeMolar Heat of Fusion The energy that must be absorbed in order to convert one mole of solid to liquid at its melting point.Molar Heat of Solidification The energy that must be removed in order to convert one mole of liquid to solid at its freezing point.
8. 8. Latent Heat of Phase Change #2Molar Heat of Vaporization The energy that must be absorbed in order to convert one mole of liquid to gas at its boiling point.Molar Heat of Condensation The energy that must be removed in order to convert one mole of gas to liquid at its condensation point.
9. 9. Latent Heat – Sample ProblemProblem: The molar heat of fusion of water is6.009 kJ/mol. How much energy is needed to convert 60 grams of ice at 0 C to liquid water at 0 C? 60 g H 2O 1 mol H 2O 6.009 kJ 20 kiloJoules 18.02 g H 2O 1 mol H 2O Mass Molar Heat of ice Mass of of water fusion
10. 10. Heat of SolutionThe Heat of Solution is the amount of heatenergy absorbed (endothermic) or released(exothermic) when a specific amount ofsolute dissolves in a solvent. Substance Heat of Solution (kJ/mol) NaOH -44.51 NH4NO3 +25.69 KNO3 +34.89 HCl -74.84