Manuale di laboratorio JoVE
Chimica
Galvanic Cells

Galvanic Cells

CONCETTI
PREPARAZIONE ISTRUTTORI
Student Protocol
Lab Manual
Chimica
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Lab Manual Chimica
Galvanic Cells

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Learning Objectives

What is electrochemistry?

Electrochemistry is a branch of chemistry that studies the relationship between a chemical reaction and electrical energy.

What are the key components of an electrochemical cell?

An electrochemical cell consists of a reaction chamber (or chambers) containing electrolyte solution(s), a salt bridge, and two conductive electrodes (the anode and cathode) that are connected electrically.

Where does oxidation and reduction occur in an electrochemical cell?

An oxidation-reduction reaction, or redox reaction, is a pair of half-reactions in which electrons are lost from one species during oxidation and gained by another species during reduction. Reduction occurs at the cathode, and oxidation occurs at the anode.

How do galvanic cells differ from electrolytic cells?

Electrolytic cells utilize electrical energy supplied from an external power source to drive a nonspontaneous reaction. In galvanic cells, a spontaneous chemical reaction generates electrical energy.

What is standard electrode potential, and how is it used in a galvanic cell?

The standard electrode potential is a measure of a substance’s tendency to lose electrons at standard conditions of 1 M, at a pressure of 1 bar, at 298 K. In a galvanic cell, the difference between the standard electrode potentials from two metals equals the voltage generated.

List of Materials

Print Materials List
  • Glass funnel
    10
  • 10-mL graduated cylinder
    5
  • 50-mL graduated cylinder
    5
  • 100-mL glass beaker
    15
  • 600-mL glass beaker
    5
  • 100-mL volumetric flask
    5
  • 20-mL volumetric flask
    5
  • 2-mL pipette controller
    5
  • 1-mL volumetric pipette
    5
  • 6-well reaction plate
    5
  • Glass thermometer
    5
  • Alligator clips
    10
  • Glass stirring rod
    5
  • Multimeter & leads
    5
  • Forceps
    5
  • 2" string soaked in KNO3
    15
  • 1 x 9 inch filter paper strips
    10
  • 1 x 2 inch emery paper strips
    10
  • 1 x 9 cm copper strips
    10
  • 2 x 6 cm lead strips
    10
  • 2 x 6 cm zinc strips
    10
  • 2 x 6 cm silver strips
    10
  • Pb(NO3)2 (minimum 0.35 g per group)
    5 g
  • CuSO4·5H2O (minimum 1.2 g per group)
    10 g
  • C2H2O4·2H2O
    10 g
  • KNO3
    4 g
  • ZnSO4·7H2O
    5 g
  • AgNO3
    10 mL
  • 250-mL glass graduated cylinder
    1
  • 500-mL glass graduated cylinder
    1
  • 250-mL Erlenmeyer flask
    3
  • 500-mL Erlenmeyer flask
    1
  • 250-mL glass bottle with cap
    1
  • Powder funnel
    1
  • 125-mL brown glass bottle with cap
    4
  • 500-mL polyethylene bottle with cap
    1
  • Magnetic stir bar
    4
  • Stir plate
    1
  • Top-loading balance
    1
  • Weighing boats
    -1 Dependent on lab size
  • Spatula
    -1 Dependent on lab size

Lab Prep

Print Setup Guide

Source: Smaa Koraym at Johns Hopkins University, MD, USA

  1. Preparation of Solutions

    Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed.

    • To set up for this lab experiment, wear the appropriate personal protective equipment, including a lab coat, chemical splash goggles, and gloves
    • 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.
    • 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.
    • 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.
    • 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.
    • Add 250 mL of deionized water to the flask and stir the solution until it appears homogeneous.
    • Transfer the solution into a labeled glass bottle and store it in the instructor's hood until the lab class.
    • 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.
    • To make 250 mL of solution, weigh 3.6 g of zinc sulfate and transfer it to an Erlenmeyer flask.
    • Add 250 mL of deionized water to the flask and set the solution on the stir plate to mix.
    • Once the solution appears homogeneous, divide it into two brown glass bottles.
    • 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.
    • 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.
    • Add 250 mL of deionized water and mix the solution until it is homogeneous.
    • 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.
  2. Preparation of Other Reagents
    • 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.
    • Each group will need about 0.35 g of lead nitrate. Place the bottle next to a balance.
    • 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.
    • Each group will also need one piece of lead. Obtain 2 x 6 cm pieces of lead and put them in a labeled beaker.
    • 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.
    • 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’.
    • Cut emery paper in 1 x 2 in pieces so that each group has two pieces.
    • Cut filter paper into 1 x 9 in pieces with one for each group.
    • 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.
    • An hour before the lab class begins, place the pieces of string in the bottle of potassium nitrate and allow them to soak.
    • Ensure that a 20-L container is dedicated to heavy metal waste and is accessible for all students in the hood.
    • 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

Tags

JoVE Lab ChemLab: 47 Prep