Experiment 17: Calorimetry

Pre- Lab Questions

  1. What is the definition of the joule in terms of the basic SI Units?
  1. A calorimeter is to be calibrated: 51.203 g of water at 55.2oC is added to a calorimeter containing 49.783 g of water at 23.5oC. After stirring and waiting for the system to equilibrate, the final temperature reached is 37.6 oC. Calculate the calorimeter constant.
  1. Use your textbook or a chemical encyclopedia to write a specific definition for the term salt.
  1. What does it mean to say that an ion becomes hydrated when a salt is dissolved in water?

Report Sheet

Part 1:

  1. Calculate the change in temperature for the hot water and for the cold water.
  1. Calculate the calorimeter constant in J/oC.
  1. Why was the calorimeter made from an insulating material like Styrofoam?
  1. What is meant by a “heat sink” in this experiment? What substance was used as the heat sink, and why?
  1. The calorie used to be used for heat measurements. Look up the value and units of a calorie with respect to joules.
  1. Calculate the calorimeter constant for your calorimeter in calories per degree Celsius.

Part 2:

  1. Calculate the average change in temperature for each solution.
  1. Calculate the average heat flow in Joules for each solution.
  1. Calculate the average enthalpy change (H) in kJ/mole for each solution.
  1. If the identity of the salts was provided by the instructor, use a chemical handbook to find the literature value for the heat of solution for your salts. Calculate the percent error between the literature value and your mean experimental value for H of solution for each of your solutions.
  1. Why is the dissolving of a salt sometimes an exothermic and sometimes an endothermic process? Were your salts exothermic or endothermic? How could you tell?