What safety equipment is required before preparing an electrolytic cell experiment?

Before beginning laboratory preparation, put on a lab coat, splash-proof safety glasses, and nitrile gloves. These protect against chemical splashes and hazardous materials. Keep baking soda readily available to neutralize any spills. Always work in a fume hood when handling concentrated solutions like copper sulfate in sulfuric acid to minimize inhalation exposure.

How is a concentrated copper sulfate solution prepared for electrolytic cell experiments?

Place a magnetic stir bar in a 6-L Erlenmeyer flask on a stir plate. Add 250 mL of sulfuric acid and 5 L of hot tap water. Turn on the stir setting and incrementally add 2.2 kg of copper sulfate, allowing each portion to dissolve before adding more. Once dissolved, add another liter of hot water and transfer the homogeneous solution to a labeled carboy for storage.

What materials and quantities are needed for each student group in an electrolytic cell lab?

Each pair of students requires 50 mL of acetone, one 1 x 9 cm copper sheet strip, one 3-inch piece of 18-gauge copper wire, one 1 by 2-inch emery paper piece, and one 10-ohm resistor. These materials are essential components for constructing and operating the electrolytic cell during the experiment.

What glassware and equipment should be set up at each lab station?

Each station needs two 50-mL beakers, one 250-mL beaker, one watch glass, one stir bar, one stir plate, disposable pipettes, a current probe and data acquisition system, three electrical wires with alligator clips, one 1.5-V battery, and one brass key. These items enable students to conduct measurements and operate the electrolytic cell safely and effectively.

Why must acetone be stored separately from other laboratory materials?

Acetone is highly flammable and must be stored in a dedicated flammables cabinet until the lab class begins. This storage requirement prevents fire hazards and ensures safe handling. Keeping flammable materials isolated from other chemicals and heat sources is a critical laboratory safety practice.

How should the copper sulfate solution be stored after preparation?

After transferring the homogeneous copper sulfate solution to a labeled 10-L carboy, cap it and store it in a corrosives cabinet until the lab begins. This storage method protects the solution from contamination and prevents accidental exposure. The carboy should remain sealed to maintain solution integrity and safety.

Electrolytic Cells

Concepts Instructor Prep Student Protocol

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Electrochemical reactions are vital to many processes in technology and the human body and involve the transfer of electrons from one chemical species to another. These reactions are called reduction-oxidation reactions or redox reactions.

When a species loses electrons, it undergoes oxidation, and we say that it is oxidized. When a species gains electrons, it has undergone reduction, and we say that it is reduced. In an electrochemical galvanic cell, redox reactions occur spontaneously, which generate electrical energy. However, in an electrolytic cell, electrical energy is applied, which causes the redox reactions to occur.

An electrolytic cell consists of the reaction solution called the electrolyte, which contains any chemical species that are oxidized or reduced as well as ions needed to enable electron flow. The electrolytic cell has two metal electrodes that are immersed in the electrolytic solution. An external circuit connects the two electrodes, which completes the circuit and enables us to apply voltage or current.

The applied current or voltage is what causes the electrochemical reaction to take place. The oxidation half-reaction occurs at the anode, and the reduction half-reaction occurs at the cathode. To help you differentiate between the two, remember the phrase 'red cat,' which stands for 'reduction at cathode'.

But how do we determine which electrode is which? We can use the standard reduction potential of the metal electrodes, which is a measure of the metal's tendency to lose electrons. The higher the reduction potential, the more likely it is for the metal to be reduced.

Let's say we place a silver electrode and a copper electrode in an electrolytic cell and apply current. The silver electrode has a higher reduction potential, so it is reduced and acts as the cathode. The copper electrode has a lower reduction potential, so it is oxidized and acts as the anode.

One use of electrolytic cells is to perform electroplating, which is a reaction where one metal is oxidized and then reduced onto the surface of another metal. Since the anode is the metal doing the plating, in our example of silver and copper, the silver electrode is plated with a thin layer of copper.

In this lab, you'll assemble an electrolytic cell and perform the electroplating process by plating a brass key with copper.

At the end of this lab, students should know...

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What is the fundamental chemical reaction in electrochemistry?

The fundamental reaction in electrochemistry is the redox, reduction-oxidation, reaction. The oxidizing agent gains electrons in the reduction half-reaction while the reducing agent loses electrons in the oxidation half-reaction.

What are the major components in an electrolytic cell?

An electrolytic cell is composed of a reaction chamber containing an electrolyte solution, two electrodes, and an external circuit connected to a power source.

At which electrode do oxidation and reduction occur?

The oxidation reaction occurs at the anode, while the reduction reaction occurs at the cathode. This can be remembered using the phrase “Red cat”: Reduction occurs at the cathode.

What is electroplating?

Electroplating is an application of the electrolytic cell. In electroplating, a metal anode is used to plate ions on the surface of a cathode, which is composed of a different material than the anode.

What parameters can be used to control the thickness of the metal being plated on the cathode?

A higher concentration of metal ions in solution, a higher applied current, and a longer plating time all increase the thickness of the plated metal on the cathode.