Experiment 14 THERMOCHEMISTRY: Heats of Reactions Experiment 14: Pre-Lab: Turn i

Question

Experiment 14 THERMOCHEMISTRY: Heats of Reactions Experiment 14: Pre-Lab: Turn in at beginning of lab 1. We wish to heat a 155.0 gram sample of an aqueous solution from 27.2°C to 82.5°C. The specific heat of the solution is known to be 3.25 J/g.C. How many kilojoules of heat will be required? 2. A 3.18 gram sample of copper metal is added to 105.5 grams of silver nitrate solution in a calorimeter. All of the copper metal reacts to form copper (II) nitrate, and metallic silver is precipitated. The original solution was at 19.5°C. The final temperature (after the reaction) is 37.5°C. Assume that the specific heat of the solution and copper combined is 3.80 J/g-°C. a. Assuming that no energy leaks from the calorimeter, how many kilojoules of heat are produced by this reaction? (Heat does actually leave the calorimeter but we assume all of the heat liberated by the reaction goes to warm the solution) b. What is the AH of reaction, expressed in kilojoules per mole of copper metal reacted? Be sure the sign of AH is correct.

Explanation / Answer

1)

mass of sample = 155.0 g

temperature rise = 82.5 - 27.2

                           = 55.3 oC

specific heat = 3.25 J / g oC

Q = m Cp dT

   = 155 x 3.25 x 55.3

Q = 27857 J

heat required = 27.86 kJ

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