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Experiment 12: The Rate and Order of a Reaction for AP Chemistry

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

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

Synopsis

The rate equation for a reaction is determined in this experiment. Known quantities of solutions are mixed, and the time required for a change is recorded. (See the Kinetics chapter.)

Equipment

      analytical balance
      buret
      clamp
      Erlenmeyer flask
      graduated cylinder
      pipet
      stopwatch
      support stand
      hermometer

Measurements

  1. Weigh solid samples.
  2. Use a pipet or a buret to measure the volume of any solutions.
  3. Use the buret to measure the volume of any gas formed (multiple measurements at different times may be required).
  4. Measure the temperature of the solutions.
  5. Measure time intervals or record the time after mixing when an observable change occurs.

NOTE: When using a buret, an initial and a final measurement are always needed.

Calculations

Using the molar mass, calculate the moles of all weighed samples. The moles of substances are converted to molarities by dividing by the volume (in liters) of the solution. Molarities may also be determined from pipet or buret readings using the dilution equation. (If a buret is used, one of the volumes is calculated from the difference between the initial and final readings.) The dilution equation may be needed to calculate the concentration of each reactant immediately after all the solutions are mixed.

If a gas is being generated, plot the volume of gas formed versus time. The volume of the gas formed is the difference between the initial buret reading and the buret reading at a particular time. The slope of this graph is the rate.

The rate may also be determined by taking the amount of any reactant divided by the time required.

Tabulate the concentrations of the reactant solutions and the rates for various trials. The rate law may be determined by comparing values in this table. (See the Kinetics chapter.)

Comments

Many types of reaction may be used. The simple recording of the time required for a noticeable change is particularly applicable to "clock" reactions.

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