Flame Test Chem 04 05

Chemistry Chapter 4 Flame Test Lab Purpose: The idea of this lab is to identify a set of flame-test color standards for selected metal ions: potassium, lithium, sodium strontium, calcium, copper, barium. Relate the colors of a flame test to the behavior of excited electrons in a metal ion. Identify three unknown metal ions by using the flame test. Materials: cotton swabs (5 or 6), mixed solutions containing the following ions: Ca, Ba, Sr, Li, Cu, K, and Na. Solutions are in dropper bottles. Bunsen burner, and tongs. Procedures: Obtain a cotton swab, and a dropper bottle containing one of the ions to be tested. Over the sink, put several drops of the test solution on the cotton swab. The swab should be saturated with solution. Light your Bunsen burner. Use tongs to hold the saturated end of the cotton swab in the hottest part of the burner flame. Observe the color produced and record your observation in the data table below. Repeat this procedure until you have tested all of the known metal ions. Repeat the procedures for the three unknowns. Record your data in the table below. Dispose of all used swabs in the garbage can.

Observations: Ion

Table of Tested Ions Using the Flame Test. Color

Ba+2 Ca+2 Cu+2 K+1 Li+1 Na+1 Sr+2

Ion present in Unknown

Unknown 1 Unknown 2 Unknown 3

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Conclusions: 1)How sensitive is the flame test. Could this be used on samples that have a low concentration of ions present? Explain your answer. (2 points) 2)What difficulties arise when trying to identify ions by the flame test? (1 point )

3)A student performed flame tests on several unknowns and observed that they all were shades of red. What should the student do to correctly identify these substances? Explain your answer. (2 points)

4)During a flood the labels from three bottles of chemicals were lost. The three unlabeled bottles of white solids were known to contain the following: strontium nitrate, ammonium carbonate, and potassium sulfate. Explain how you could easily test the substances and relabel the three bottles. (3 points)

5)Some stores sell “fireplace crystals”. When sprinkled on a log, these crystals make the flames blue, red, green, and violet. Explain how these crystals can change the flame’s color. What ingredients do you expect them to containn? (5 points)

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