Purpose: The purpose of the “Properties of Hydrates” lab is to study hydrates, and be able to identify them. This lab also focuses on observing the reversibility of hydration reactions by hydrolysis, and also testing substances for efflorescence of deliquescence.
A. Identification 1. Place 0.5 grams of each compound (Nickel Chloride, Potassium Chloride, Sodium Tetraborate, Sucrose, Calcium Carbonate, and Barium Chloride) in a small dry test tube. 2. Heat gently with a burner flame and observe carefully. If droplets of water appear on the test tube it may be a hydrate. Note the nature and color of the residue. 3. Let the tube cool, and try to dissolve the residue in a few cm3 of water, warming if necessary. A true hydrate will dissolve in water, producing a color similar to that of the original hydrate. A carbohydrate will give off water, but tends to char. The residue will also often be a caramel color.
B. Reversibility 1. Gently heat a few crystals of about 0.3 grams of hydrated Cobalt(II) Chloride, CoCl2 x 6H2O in an evaporating dish until the color change appears to be complete 2. Dissolve the residue in the evaporating dish in a few cm3 of water from the wash bottle 3. Heat the residue to a boiling and carefully boil it to dryness. Note any color changes. 4. Put the evaporating dish on the lab bench and let it cool.
C. Deliquescence and Efflorescence 1. Place a few crystals of Na2CO3 x 10H2O, CaCl2, KAl(SO4)2 x 12 H20, and CuSO4 in an a separate evaporating dish next to the CoCl2 prepared in part B. 2. To see weather the samples gained or lost mass, weigh each of them on a top-loading balance and record to the nearest hundredth. 3. Weight them again after an hour to detect ANY changes in mass. 4. Observe the samples occasionally. Note any structures in color and structure and degree of wetness.
D. Percent of Water in Hydrate 1.