Date Preformed: 3/19/2012
Date Submitted: 3/26/2012
Lab Partners: Anita Smith, Taylor Bell, Derek Bourgeois
a.To determine the percent of copper and the formula weight of a copper compound.
a.Magnesium is a very active metal which can reduce copper (II) ions in a weight sample of a compound to metallic copper. The reduction of copper ions in a compound to a copper metal is caused by the addition and oxidation of magnesium. The reaction takes place in an aqueous solution of a weighed sample of a copper-containing salt. Magnesium completely displaces copper from the solution allowing for measurements. Hydrochloric acid is then added to dissolve the excess magnesium which also produces hydrogen gas. HCl does not react with copper. The metallic copper can be filtrated and then weighed so that the percent of copper can then be calculated.
a.Receive a test tube from your teacher with approximately 2 grams of a unknown copper compound and record the identity number. b.Wash 2 150 mL beakers and rinse with distilled water.
c.Weigh the test tube and the total unknown and record the mass in grams. d.Tap about half of the unknown sample into one of the 150 mL beakers and label beaker # 1. e.Weigh the test tube and the remainder of the unknown and record the mass in grams. f.Empty the reminder of the unknown into the second 150 mL beaker and label beaker # 2. g.Weigh the empty test tube and record the mass in grams.
h.Place a clean stirring rod fitted with a rubber tip in each beaker. i.Add about 50 mL of distilled water to each beaker.
j.Add 5 mL of 6 M HCl to each beaker. Stir until the solid salt has dissolved. If the solid remains after stirring add 6 M HCl in 2 mL increments until solid is dissolved. k.Add 0.4 g of magnesium turnings to each beaker and stir well. Stir frequently for at least 15 minutes....