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Experiment 13: Enthalpy Changes for AP Chemistry

By — McGraw-Hill Professional
Updated on Feb 8, 2011

For a quick review on stoichiometry, refer to the following concepts:

Synopsis

In this experiment the heat change associated with a process is calculated. Various substances are added to a calorimeter (usually a polystyrene cup), and the initial and the final temperatures are measured. (See the Stoichiometry chapter.)

Equipment

      analytical balance
      calorimeter
      graduated cylinder
      thermometer

Measurements

  1. The masses of various substances are determined
  2. The volume of a solution or solvent is determined with a graduated cylinder.
  3. Measure the initial temperature.
  4. Measure the final temperature.

Calculations

The masses are converted to moles using the molar mass. The volumes of solutions may be converted to moles using the molarity.

The mass of a solvent or solution may be calculated from the volume and density.

A total mass may need to be calculated by adding the individual masses together.

The change in temperature (ΔT) is calculated from the difference between the final and initial temperatures.

The energy (joules or calories) is calculated by multiplying the mass times the change in temperature times the specific heat (from a table).

The enthalpy change is calculated by dividing the calculated energy by the moles, mass, or some other designated quantity.

Comments

Any reaction or phase change may be used.

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