STOICHIOMETRY

Stoichiometry

Lab Report

Introduction

You are about to enter the exciting world of copper chemistry. A small quantity of copper will be carried through the following transformations:

Cu ? Cu(NO3)2 ? Cu(OH)2 ? CuO ? CuCl2 ? Cu3(PO4)2 ? CuSO4 ? Cu

Not only will this lab teach you much about chemistry, it also gives you practice in many of the laboratory skills we have learned during the course of the year. Most of the labs we have done this year have been completed in one or two lab periods. In the real world, a chemist may work on a problem for months or years. This lab will take 4-5 class periods. Choosing the wrong place to stop will extend the time to six class periods, so watch the directions for suggested stopping places.

Safety

Copper sulfate is a skin and respiratory irritant. It is toxic by ingestion and inhalation. Wear goggles at all times. Be sure to wash your hands thoroughly at the end of the experiment.

Use caution when working with the Bunsen burner. Tie back hair and secure loose clothing. Do not reach over the flame, and never leave your lit burner unattended. If you are unable to light the burner within 10 seconds, shut off the gas, wait 10 seconds, and try again.

Materials

crucible & cover

crucible tongs

dropper

ring stand

stirring rod

spatula

watch glass

wire gauze

Clay triangle

Bunsen burner

CuSO4•5H2O

Procedure

Measure the mass of the empty crucible and record the mass in the Data Table. You will need this information later.

Place the empty crucible on the balance pan and then press the tare button. Once you see all zeros, carefully add about between 4.80-5.20 grams of the hydrate and record the exact mass of hydrate in the Data Table.

Set up the ring stand, iron ring, clay triangle, Bunsen burner, and crucible as shown in the picture below. Position the cover of the crucible slightly tipped, leaving only a small opening for gases to escape.

Heat the crucible and its contents with the Bunsen burner for ten minutes on medium to high heat or until all of the blue color has disappeared.

Start with a low blue flame and gradually increase the heat applied.

During the heating, use a metal scoopula or glass stirring rod to break up any large clumps of hydrate. Try not to pick up any of the solid on the spatula/stirring rod.

If the edges of the solid appear to be turning brown, remove the heat momentarily and resume heating with a cooler flame.

Using crucible tongs with both hands, remove the crucible from the apparatus. Place it on a square of wire gauze, so that it is not in contact with the table. Allow the crucible to cool for several minutes.

After cooling, immediately find the mass of the crucible + the anhydrous salt, and record it in the Data Table. The anhydrous compound must be weighed before the compound reabsorbs water from the atmosphere.

When you have finished, scrape the anhydrous salt out of the crucible onto a watch glass. Use a dropper to place a few drops ...