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E. Calorimetry q = m C T q = heat or enthalpy J m = mass g C = specific heat J/g°C T = temperature change °C Note – these problems could also be done in calories q sys = - q surr
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Tells how much heat is required to change the temp of a substance. Some specific heats are Al0.902 J/g o C Cu0.385 J/g o C H 2 O4.184 J/g o C Quantity of heat supplied Temperature change (always Tf-Ti)
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A 55.0 g piece of metal was heated in boiling water to a temperature of 99.8 o C and dropped into an insulated beaker with 225 mL of water (d = 1.00 g/ml) at 21.0 o C. The final temperature of the metal and water is 23.1 o C. Calculate the specific heat of the metal assuming that no heat was lost to the surroundings.
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1. Pressure Constant (Coffee Cup) Calculate H rxn in kJ/mol when mixing: 50 mL of 0.10M AgNO 3 50 mL of 0.10M HCl in a coffee cup calorimeter. The temperature rises from 22.3 °C to 23.1 °C. AgNO 3(aq) + HCl (aq) AgCl (aq) + HNO 3(aq)
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2. Volume Constant (Bomb Calorimeter) q rxn = - C bomb T C bomb is an experimentally determined value using a known material. Each calorimeter has its own constant value!!
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2. Volume Constant (Bomb Calorimeter) Octane, C 8 H 18, a primary constituent of gasoline, burns in air. 2 C 8 H 18(l) + 25 O 2(g) 16 CO 2(g) + 18 H 2 O (l) Suppose that a 1.00 g sample of octane is burned in a calorimeter that contains 1.20 kg of water. The temperature of the water and the bomb rises from 25.00 o C to 33.20 o C. If the specific heat of the bomb, C bomb, is known to be 837 J/ o C, calculate the molar heat of reaction of C 8 H 18.
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