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Calorimetry. Chapter 5. Calorimetry. Since we cannot know the exact enthalpy of the reactants and products, we measure H through calorimetry , the measurement of heat flow. Calorimetry Functions. Can be used to determine: Heat capacities

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## Calorimetry

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**Calorimetry**Chapter 5**Calorimetry**Since we cannot know the exact enthalpy of the reactants and products, we measure H through calorimetry, the measurement of heat flow.**Calorimetry Functions**• Can be used to determine: • Heat capacities • Enthalpies of vaporization (amount of heat required to change from a liquid to a gas) • Enthalpies of fusion (amount of heat lost to change from a liquid to a solid) • Enthalpies of chemical reactions (how much heat is gained or lost from a reaction)**Heat Capacity and Specific Heat**The amount of energy required to raise the temperature of a substance by 1 K (1C) is its heat capacity. We define specific heat capacity (or simply specific heat) as the amount of energy required to raise the temperature of 1 g of a substance by 1C (1 K).**Heat**q = m*c*ΔT q= heat m= mass c= specific heat ΔT= final – initial temperature**Heat Capacity and Specific Heat**Specific heat, then, is heat transferred Specific heat = mass temperature change q c = m T**Constant Pressure Calorimetry**By carrying out a reaction in aqueous solution in a simple calorimeter such as this one, one can indirectly measure the heat change for the system by measuring the heat change for the water in the calorimeter.**Constant Pressure Calorimetry**Because the specific heat for water is well known (4.184 J/mol-K), we can measure H for the reaction with this equation: q = m c T**Calorimetry Concepts**• Heat is always transferred from warmer object to cooler object • If two object do not have the same specific heat, they will not have the same changes in temperature • Law of Conservation of Energy applies to heat transfer. • Heat lost by object 1 is the amount of heat gained by object 2. • Heat is not the same thing as temperature.**Practice Problem**If the temperature of a 34.4 g of ethanol increases from 25.0°C to 78.8°C, how much heat has been absorbed by the ethanol (specific heat of ethanol= 2.46 J/g*°C)?**Practice Question**If a 50.0 g unknown metal with a temperature of 115.0°C, is placed in 125 g of 25.6°C water in a foam cup calorimeter and the metal causes the water to raise it’s temperature to 29.3°C, what is the specific heat of the metal? Part 1: solve the heat the water gained Part 2: heat gained by water = heat lost by metal Part 3: Using the change in temperature of the metal = final T of water – initial T of metal

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