Calorimetry - temperature change ( T ) that a known mass (...

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Calorimetry Experimentally, we can determine the heat flow ( H rxn ) associated with a chemical reaction by measuring the temperature change it produces . The measurement of heat flow is called calorimetry An apparatus that measures heat flow is called a calorimeter Heat capacity and specific heat The temperature change experienced by an object when it absorbs a certain amount of energy is determined by its heat capacity . The heat capacity of an object is defined as the amount of heat energy required to raise its temperature by 1 K ( or °C ) The greater the heat capacity of an object, the more heat energy is required to raise the temperature of the object For pure substances the heat capacity is usually given for a specified amount of the substance The heat capacity of 1 mol of a substance is called its molar heat capacity The heat capacity of 1 gram of a substance is called its specific heat The specific heat of a substance can be determined experimentally by measuring the
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Unformatted text preview: temperature change ( T ) that a known mass ( m ) of the substance undergoes when it gains or loses a specific quantity of heat ( q ): 209 J of energy are required to increase the temperature of 50.0 g of water by 1.00 K. What is the specific heat of water? Specific heat values of some substances (J g-1 K-1 ) Al (s) 0.90 CaCO 3 (s) 0.85 C (s) 0.71 CCl 4 (l) 0.86 Fe (s) 0.45 H 2 O (l) 4.18 Hg (l) 0.14 We can calculate the quantity of heat that a substance has gained or lost by using its specific heat together with its measured mass and temperature change: rearrange: How much heat is required to raise the temperature of 250g of water from 22 C to 98 C? (specific heat of water is 4.18 J g-1 K-1 ). q = (4.18 J g-1 K-1 )*(250g)*(371-295 K) q = 79,420 J (79.420 kJ, or 7.942 x 10 4 J) What is the molar heat capacity of water? Molar heat capacity = 4.18 J g-1 K-1 * (18 grams/1.0 mole) = 75.2 J mole-1 K-1...
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Calorimetry - temperature change ( T ) that a known mass (...

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