18 Questions
What is the electrode called that is sensitive to the analyte's concentration?
Working electrode
Which electrode serves to provide a reference potential against which the working electrode's potential is measured?
Counter electrode
In a dynamic method, what electrode may change its potential over time due to the passage of current?
Counter electrode
What instrument is used to measure the potential of an electrochemical cell under zero current conditions?
Potentiometer
Which type of instrument is used when it is necessary to control the current flowing through an electrochemical cell?
Galvanostat
When it is necessary to control the potential of the working electrode in dynamic methods, what instrument is typically used?
Potentiostat
What is the main purpose of an electrolytic cell?
Use electricity to drive non-spontaneous chemical reactions
Where does oxidation occur in an electrochemical cell?
Anode
What is the purpose of a cathode in a voltaic cell?
To gain electrons during reduction reactions
How do voltaic cells differ from electrolytic cells?
Voltaic cells convert chemical energy into electrical energy, while electrolytic cells do the opposite
Which electrode is responsible for gaining electrons in an electrochemical cell?
Cathode
What is the function of an anode in a voltaic cell?
Undergo oxidation reactions by losing electrons
What is the purpose of dividing the electrochemical cell into two half-cells?
To prevent the redox reaction from occurring spontaneously
What is the function of the salt bridge in a potentiometric electrochemical cell?
To complete the electric circuit by allowing ions to move between half-cells
In a potentiometric electrochemical cell, which electrode is considered to be the cathode?
The electrode on the right
Why are porous frits used at the ends of the salt bridge?
To allow ions to move freely while preventing the mixing of solutions
Which half-cell in a potentiometric electrochemical cell is typically designated as the reference electrode?
The anode (left half-cell)
What is the role of the indicator electrode in a potentiometric electrochemical cell?
To measure changes in cell potential
Study Notes
Electrochemical Cells
- Electrochemical cells are special containers used to either generate electricity from chemicals or use electricity to facilitate chemical reactions.
- There are two main types: voltaic (galvanic) cells and electrolytic cells.
Voltaic Cells
- Also known as tiny power plants, they convert chemical reactions into electrical energy.
- Examples include batteries in cars and flashlights.
Electrolytic Cells
- They use electricity to facilitate chemical reactions that wouldn't occur naturally.
- An example is using electricity to split water into oxygen and hydrogen gas.
Electrodes
- Anode: where oxidation (losing electrons) occurs.
- Cathode: where reduction (gaining electrons) occurs.
Potentiometric Electrochemical Cells
- A typical cell consists of two half-cells, each containing an electrode immersed in a solution with ions that determine the electrode's potential.
- The half-cells are separated by a salt bridge containing an inert electrolyte, such as KCl.
- The salt bridge connects the two half-cells, allowing ions to move freely and completing the electric circuit.
Electrode Roles
- By convention, the electrode on the left is the anode (where oxidation occurs), and the electrode on the right is the cathode (where reduction occurs).
- In potentiometric electrochemical cells, the indicator electrode is the cathode (right half-cell), and the reference electrode is the anode (left half-cell).
Measuring Electrochemical Cells
- Potentiometers: measure the potential of an electrochemical cell under conditions of zero current.
- Galvanostats: used for dynamic methods, such as constant-current coulometry, to control the current flowing through an electrochemical cell.
- Potentiostats: used for dynamic methods to control the potential of the working electrode.
Test your knowledge on the components of an electrochemical cell such as working electrode and counter electrode. Learn how these electrodes work together to measure the potential of analytes. Explore the importance of maintaining a constant potential in the counter electrode.
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