9.7 Electrolysis and Faraday's Laws

• Electrolysis is the process of using an electric current to drive a non-spontaneous chemical reaction.
• Steps in the electrolysis process:

  1️⃣ Prepare electrodes

  2️⃣ Set up the electrolytic cell

  3️⃣ Apply external voltage

  4️⃣ Redox reactions occur
• Match the variable in Faraday's First Law with its meaning and units:

  m ↔️ Mass of substance in grams

  Q ↔️ Quantity of electricity in coulombs

  k ↔️ Constant of proportionality in g/C
• What is electrolysis used to drive?

  Non-spontaneous chemical reactions
• What does an electrolyte solution contain?

  Ions that conduct electricity
• The electrolyte in electrolysis provides ions for oxidation and reduction at the electrodes.


  True
• Faraday's First Law states that the mass of a substance deposited or liberated during electrolysis is directly proportional to the quantity of electricity passed through the electrolyte.
• Electrolysis is defined as using an electric current to drive a non-spontaneous chemical reaction.
• The external voltage required for electrolysis must exceed $\frac{\Delta G}{nF}$.


  True
• The flow of electrons through the electrolyte is called an electric current
• Faraday's constant is approximately 96485 C/mol.
• Where does oxidation occur in electrolysis?

  At the anode
• The constant of proportionality in Faraday's First Law has units of g/C.

  True
• Match the electrolysis component with its function:

  Electrolyte ↔️ Provides ions for redox

  Electrodes ↔️ Serve as interfaces for redox

  External voltage ↔️ Supplies energy for reactions
• Faraday's First Law can be mathematically expressed as m = kQ</latex>.


  True
• Faraday's constant ($F$) is approximately 96485 C/mol.


  True
• The Gibbs free energy change ($\Delta G$) represents the energy needed to drive a non-spontaneous reaction.


  True
• An external voltage provides the energy for redox reactions in electrolysis.

  True
• Faraday's First Law states that the mass of a substance deposited is directly proportional to the quantity of electricity
• Match the variables in Faraday's Second Law with their meanings:

  m ↔️ Mass of substance

  E ↔️ Equivalent weight
• The equivalent weight of a substance is always less than its molar mass.

  True
• Match the variables with their meanings:

  $m_{1}$ ↔️ Mass of substance 1

  $E_{2}$ ↔️ Equivalent weight of substance 2

  $m_{2}$ ↔️ Mass of substance 2

  $E_{1}$ ↔️ Equivalent weight of substance 1
• Steps to calculate quantities in electrolysis using Faraday's Laws

  1️⃣ Identify key variables such as mass, moles, charge, and current

  2️⃣ Convert time to seconds and use the formula $Q =$$It$ to find the charge

  3️⃣ Determine the moles of electrons involved from the redox reaction

  4️⃣ Use Faraday's constant to find the moles of substance

  5️⃣ Calculate the mass using the molar mass of the substance
• In the reduction of Cu^{2 + }</latex> to $Cu$, two moles of electrons are required to deposit one mole of copper
• Match the laws with their formulas:

  Faraday's First Law ↔️ $m =$$kQ$

  Faraday's Second Law ↔️ $\frac{m_{1}}{m_{2}} =$$\frac{E_{1}}{E_{2}}$
• An electric current in electrolysis is the flow of electrons through the electrolyte.


  True
• What is the function of electrodes in electrolysis?

  Provide oxidation and reduction interfaces
• Electrodes in electrolysis are typically made of conductive materials like metal or carbon.


  True
• The external voltage in electrolysis must exceed the Gibbs free energy change divided by the product of moles of electrons transferred and Faraday's constant.

  True
• Why is an external voltage applied in electrolysis?

  To overcome energy barrier
• What does Faraday's First Law state about electrolysis?

  Mass is proportional to charge
• What does Faraday's Second Law state about electrolysis?

  Masses are proportional to equivalent weights
• The quantity of electricity passed is calculated using the formula $Q =$$It$, where $I$ is the current.
• What is the value of Faraday's constant?

  $96485$ C/mol
• Two moles of electrons are required to deposit one mole of copper from $Cu^{2 + }$ ions.


  True
• Faraday's Second Law is represented by the formula \frac{m_{1}}{m_{2}} = \frac{E_{1}}{E_{2}}</latex>, where $E$ is the equivalent weight.
• Steps to solve electrolysis problems using Faraday's Laws

  1️⃣ Identify key variables: mass, moles, charge, current

  2️⃣ Determine the charge using $Q =$$It$

  3️⃣ Find moles of electrons transferred from the redox reaction

  4️⃣ Use Faraday's constant to calculate moles of substance

  5️⃣ Calculate mass using $m =$$n \times \text{Molar Mass}$
• What is the relationship between the masses of substances and their equivalent weights in Faraday's Second Law?

  Proportional
• Faraday's Second Law can be mathematically expressed as $\frac{m_{1}}{m_{2}} =$$\frac{E_{1}}{E_{2}}$.


  True
• Faraday's Second Law compares the masses of different substances deposited by the same quantity of electricity.


  True