Properties of Group IA and IIA Salts
Many of the alkali and alkaline earth metal salts are white crystalline solids. However, these salts have many chemical and physical properties which distinguish them from one another. In this experiment you will work with the following five salts:
barium sulfate strontium chloride
calcium carbonate sodium sulfite
potassium chloride
Each of these compounds is white, but you will perform four simple tests which will allow you to distinguish between them. After running the tests on these compounds, you will obtain an unknown (one of the five salts) which you will be asked to identify. The four tests you will use to distinguish the salts are: the solubility in water, the effect of dilute acid, the effect of dilute base, and a flame test.
Procedure
From the reagent bottles, obtain about a teaspoonful of each salt (you may use your 3 smallest beakers and two weighing boats as your containers). Be sure to label your containers. If the particles of the solids are large, they may take a long time to dissolve. You may want to crush the particles with your spatula or glass rod.
1. Solubility in water - Fill a 13 x 100 mm test tube one-third full of water and add to it a small portion of the substance to be tested with your spatula. Use only a small portion on the small tip of your spatula. Be sure to use the same amounts for each substance. Some substances dissolve slowly so wait a few minutes and record on your data sheet whether or not the salt is soluble.
2. Effect of dilute acid - Check the effect of dilute nitric acid (HNO3) on each salt by filling a 13 x 100 mm test tube one-third full with the acid and adding a small sample of salt from your spatula. Record the solubility or reactivity of the salt (note bubbles, heat, change of color, etc.)
3. Effect of dilute base - Determine the effect of dilute base on the salts by adding a few crystals with your spatula to a 13 x 100 mm test tube which is one-third full of dilute sodium hydroxide (NaOH). Record the results.
4. Flame test - Many of the alkali and alkaline earth metal salts give colored flame tests that are characteristic of the metal ion present. Take a small amount of the salt on the nicrome wire as directed by your instructor and test it in the Bunsen burner flame. Record the color (if any) of the flame which appears.
Finally, obtain an unknown sample from the stockroom and repeat the tests above. Compare your results for the unknown to the known salts to identify your sample.
Date ______Name ______
Barium Sulfate
BaSO4
Calcium Carbonate
CaCO3
Potassium Chloride
KCl
Sodium Sulfite
Na2SO3
Strontium Chloride
SrCl2
Unknown
The identity of unknown # ______is ______.
Briefly explain your reasoning.