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Extra Calorimetry and Enthalpy Questions

# Extra Calorimetry and Enthalpy Questions - Extra...

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Extra Calorimetry Questions If a gold ring with a mass of 5.5 g changes in temperature from 25.0 to 28.0 o C, how much energy (in joules) has it absorbed? Hint: look up the specific heat capacity of gold. (2.1 J) The temperature of a 250 g sample of water changed from 25.0 to 30.0 o C. How much energy was transferred into the water to cause this change? Calculate your answer in joules, kilojoules, calories, and kilocalories. (5.2 x 10 3 J, 5.2 kJ, 1.2 x 10 3 cal, 1.2 kcal) A 1.32 g sample of sucrose, C 12 H 22 O 11 , is burned in the presence of excess oxygen in a bomb calorimeter. The heat capacity of the calorimeter had previously been found to be 9.43 kJ/ o C. The heat liberated by the combustion in the bomb caused in the bomb caused the temperature of the calorimeter’s contents to change from 25.00 to 27.32 o C. Calculate the heat of combustion per mole of sucrose in units of kJ/mol. (5.67 x 10 3 kJ/mol) Gram for gram, fats in food have much more chemical energy than sugar. One component of fat is stearic acid, C 18 J 36 O 2 . When a 1.02 g sample of stearic acid was burned completely in a bomb calorimeter, the temperature of the calorimeter rose by 4.26 o C. The heat capacity of the calorimeter was 9.43 kJ/ o C. Calculate the heat of combustion of stearic acid in kilojoules per mole. (1.12 kJ/mol) The reaction of the hydrochloric acid and sodium hydroxide is exothermic. The equation is HCl ( aq ) + NaOH( aq ) NaCl( aq ) + H 2 O In one experiment, a student placed 50.0 mL of 1.00 M HCl at 25.5 o C in a coffee cup calorimeter. To this was added 50.0 mL of 1.00 M NaOH solution also at 25.5 o C. The mixture was stirred, and the temperature quickly increased to a maximum of 32.4 o C. What is the heat of reaction in joules per mole of HCl? (Some assumptions that you would be expected to make: Because the solutions are relatively dilute, we can assume that their specific heats are close to that of water, 4.18 J/ (g o C), and that their densities are 1.00 g/ mL. We also assume that no heat is lost to the coffee cup itself or to the surrounding air.) (58 kJ/mol) When pure sulfuric acid dissolves in water, a great deal of heat is given off. To measure it, 175 g of water was placed in a coffee cup calorimeter and chilled to 10.0 o C, was added, and the mixture was quickly stirred with a thermometer.

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