Topic 24 Electrochemistry. Flashcards
Describe the process of electrolysis and its components.
Electrolysis is the process of decomposition a molten or aqueous ionic compound, known as an electrolyte, into its elements by passing an electric current through it.
This process requires two electrodes: a cathode (negative electrode) where reduction occurs, and an anode (positive electrode) where oxidation takes place.
Explain the significance of the Faraday constant in electrolysis.
The Faraday constant (F) quantifies the amount of electric charge needed to transfer one mole of electrons.
It is defined as F = Le, where L is Avogadro’s constant (approximately 6.02 x 10^23 particles per mole) and e is the charge of an electron (in coulombs).
The value of 1 Faraday is approximately 9.65 x 10^4 C mol^-1.
How do cations and anions behave during electrolysis?
During electrolysis, cations (positive ions) migrate towards the cathode, where they gain electrons and are reduced to form neutral atoms.
Conversely, anions (negative ions) move towards the anode, where they lose electrons and are oxidized to form neutral atoms.
Define the electrochemical series and its relevance in electrolysis.
The electrochemical series ranks elements by their standard electrode potentials, showing their tendency to gain or lose electrons.
In electrolysis, metal ions below hydrogen in the series deposit at the cathode, while those above cause hydrogen gas to form instead.
Describe the reactions occurring during the electrolysis of aqueous NaCl.
In the electrolysis of aqueous sodium chloride (NaCl), the reactions at the electrodes involve the movement of sodium ions (Na+) and chloride ions (Cl-).
At the cathode, sodium ions gain electrons to form sodium metal: Na+ + e- → Na.
At the anode, chloride ions lose electrons to form chlorine gas: 2Cl- → Cl2 + 2e-.
Explain how to calculate the amount of charge passed during electrolysis.
To calculate the amount of charge passed during electrolysis, you can use the formula Q = It, where Q is the charge in coulombs, I is the current in amps, and t is the time in seconds.
First, multiply the current by the time to find the total charge in coulombs.
Then, to convert this charge into faradays using the formula Q = n x F.
Where:
- Q is the total charge in coulombs (C)
- n is the number of Faradays
- F is the value of 1 Faraday where 1 Faraday = 9.65 x 10^4 C/mol.
Define the relationship between coulombs and faradays in electrolysis calculations.
In electrolysis calculations, the relationship between coulombs and faradays is defined by the Faraday constant, which states that 1 faraday is equivalent to approximately 96500 coulombs.
This means that for every faraday of charge passed, one mole of electrons is transferred.
Therefore, to convert coulombs to faradays, you divide the total charge in coulombs by 96500.
Define standard cell potential.
Standard cell potential (E° cell) is the voltage produced by an electrochemical cell under standard conditions (1M concentration, 1 atm pressure, and 25°C).
It is calculated as the difference between the standard reduction potentials of the cathode and anode:
E° cell = E° cathode - E° anode.
Explain the significance of standard electrode potential in electrochemistry.
Standard electrode potential (E°) is a measure of the tendency of a half-cell to gain or lose electrons when it is in contact with its ion in a solution, under standard conditions (1M concentration, 1 atm pressure, and 25°C).
It indicates the tendency of a species to gain electrons and be reduced.
A higher E° value signifies a greater likelihood of reduction, thus allowing for predictions about the direction of electron flow in electrochemical cells and the feasibility of redox reactions.
Define the Nernst equation and its application in electrochemistry.
The Nernst equation relates the cell potential of an electrochemical cell to the concentrations of the reactants and products involved in the redox reaction. It is expressed as E = E° + (0.059/z) log [oxidised species] / [reduced species].
This equation is essential for calculating the cell potential under non-standard conditions.
