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Online Chemistry Labs | Learning Objectives

Background:

This experiment introduces the student to analytical electroplating. The plating power supply passes a fixed current for a predetermined time through each of three aqueous solutions of unidentified metallic salts to plate metal on a platinum basket. The mass gained due to a known quantity of charge is determined, and the student also notes the color of the plated metal. After removing the plated metal with an acid bath, the student repeats each run. Although the number of electrons required to plate a given metal ion is not known, the ratio of mass plated per mol of electrons may be compared with theoretical values for a list of specific elements, and the student can identify the likely metals, using solution color and metal color for confirmation. Plating efficiency is discussed and is expected to be near 100%.

 Electroplating

Learning Objectives:

  1. Study the design and function of an electroplating apparatus.
  2. Be able to perform a series of plating runs to produce measurable plated mass.
  3. Be able to identify three unknown ions from measured mass per mole of electrons using literature values and Faraday's Law.
  4. Be able to calculate plating efficiency, given that the value will be close to 100%.
  5. Be able to answer questions involving possible sources of error and predict side reactions in the case of an element which cannot be reduced to metal in aqueous solution.