Jove Lab Chem
Galvanic Cells — Lab Prep
Source: Smaa Koraym at Johns Hopkins University, MD, USA
- Preparation of Solutions
Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.
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To set up for this lab experiment, wear the appropriate personal protective equipment, including a lab coat, chemical splash goggles, and gloves
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Prepare 0.1 M oxalic acid dihydrate. Each group will need 50 mL. For 500 mL of solution, weigh 6.304 g of oxalic acid, and transfer it to an Erlenmeyer flask. Note: Oxalic acid is corrosive, so use caution while handling.
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Measure 500 mL of deionized water, and pour it into the flask. Add a stir bar and set the flask onto a stir plate. Turn on the stir setting and allow the solution to mix until it is homogeneous.
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Obtain a polyethylene bottle with a cap and label it. Use a powder funnel to transfer the solution to the bottle, cap it, and store it in the instructor's hood until the lab.
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Prepare a 0.1 M potassium nitrate solution, which will be used to soak the strings for the salt bridge. To make 250 mL of solution, weigh 2.53 g of potassium nitrate and transfer it to a flask.
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Add 250 mL of deionized water to the flask and stir the solution until it appears homogeneous.
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Transfer the solution into a labeled glass bottle and store it in the instructor's hood until the lab class.
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Prepare a 0.05 M zinc sulfate solution, which will be used as an unknown solution in the experiment. Each group will need 8 mL of solution, so calculate how much you will need to make for your class.
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To make 250 mL of solution, weigh 3.6 g of zinc sulfate and transfer it to an Erlenmeyer flask.
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Add 250 mL of deionized water to the flask and set the solution on the stir plate to mix.
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Once the solution appears homogeneous, divide it into two brown glass bottles.
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Label one of the bottles as ‘unknown number 1’, and the other as ‘unknown number 3’. Store the bottles in the instructor's hood until the lab.
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Prepare 0.22 M silver nitrate, which will also be used as an unknown solution in the experiment. Each group will need 8 mL. To prepare 250 mL of solution, weigh 9.34 g of silver nitrate, and transfer it to the flask.
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Add 250 mL of deionized water and mix the solution until it is homogeneous.
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Then, transfer the solution to two brown glass bottles. Label them ‘unknown number 2’ and ‘unknown number 4’. Store the bottles with the other prepared solutions in the instructor's hood.
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- Preparation of Other Reagents
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Each group will need about 1.25 g of copper sulfate. Place the bottle next to the analytical balance along with a clean spatula and weigh boats.
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Each group will need about 0.35 g of lead nitrate. Place the bottle next to a balance.
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You'll also need 1 x 9 cm pieces of copper sheet. Count out enough for each group to have two pieces and place them in a container.
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Each group will also need one piece of lead. Obtain 2 x 6 cm pieces of lead and put them in a labeled beaker.
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Obtain 2 x 6 cm pre-cut pieces of zinc sheet, one for each group. Divide the strips into two beakers with one labeled as unknown number 1 and the other as unknown number 3.
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Each group will also need one 2 x 6 in piece of silver sheet. Divide the strips into two beakers with one labeled as ‘unknown number 2’, and the other as ‘unknown number 4’.
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Cut emery paper in 1 x 2 in pieces so that each group has two pieces.
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Cut filter paper into 1 x 9 in pieces with one for each group.
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Cut pieces of string 2 in long. Each group will need three pieces of string, so cut as many as are needed for the class size.
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An hour before the lab class begins, place the pieces of string in the bottle of potassium nitrate and allow them to soak.
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Ensure that a 20-L container is dedicated to heavy metal waste and is accessible for all students in the hood.
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Set out the remaining equipment and glassware at each lab station (we suggest that students work in pairs):
1 Multimeter with red and black leads 2 Alligator clips 1 Glass thermometer 1 6-well reaction plate 1 Pair of forceps 1 20-mL volumetric flask 1 100-mL volumetric flask 1 1-mL volumetric pipette 1 2-mL capacity pipettor 3 100-mL beakers 1 10-mL graduated cylinder 1 50-mL graduated cylinder 1 600-mL beaker 2 Glass funnels
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