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Calorimetry

Calorimetry. Calculating Heat. Q can be found experimentally by measuring the heat flow accompanying a reaction This is done by measuring temperature This process is called calorimetry. Specific Heat (c). This is amount of heat required to raise the temperature of 1g of a substance 1 ºC

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Calorimetry

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  1. Calorimetry

  2. Calculating Heat • Q can be found experimentally by measuring the heat flow accompanying a reaction • This is done by measuring temperature • This process is called calorimetry

  3. Specific Heat (c) • This is amount of heat required to raise the temperature of 1g of a substance 1ºC • Specific heat is different for different substances • A lower specific heat means that it takes a small amount of heat to change the substance’s temperature

  4. Calculating the Heat Transfer • Heat transfer can be calculated using Q = (c)(m)(Δt) • The specific heat of iron(III) oxide is .75 J/g ºC. What is the heat required to increase the temperature of a 1.75 g sample from 25ºC to 380ºC?

  5. Enthalpy (ΔH) • ΔH is Q at a constant pressure • ΔH is always the J given off per mole of reactant (J/mol)

  6. Example • When 50 ml of a 1.0 M HCl and 50 ml of a 1.0 M NaOH solution are mixed, the temp in a calorimeter increases from 21.0 ºC to 27.5ºC. The total volume of the end solution is 100 ml, its density is 1.0 g/ml, and its specific heat is 4.18 J/gºC. Find the enthalpy change (heat of reaction)?

  7. Water Chamber Calorimetry • Heat lost by a reaction is gained by a quantity of water in a calorimeter • Heat lost = Heat gained • C(water) = 4.184 J/gºC

  8. Example • In a calorimeter containing 100 g of water at 21ºC, a reaction is carried out in which 3.5 g of NH4NO3 decomposes into N2O and H2O. The temperature raises to 25ºC. Find the heat of reaction.

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