Electrode Potentials and Cells

• What type of reactions do electrochemical cells use?

  Redox reactions

  
• What creates a flow of electrons in electrochemical cells?

  The electron transfer between products
• What is produced between the two electrodes in an electrochemical cell?

  A potential difference
• What are the main components of most electrochemical cells?

  Two solutions with metal electrodes and a salt bridge

  
• What is the function of a salt bridge in an electrochemical cell?

  To carry the flow of charge without interfering with the reaction
• What is a half-cell in the context of electrochemical cells?

  A solution that makes up part of the full chemical cell
• What does the cell potential indicate in a half-cell?

  How it will react, either as an oxidation or reduction reaction

  
• What are the specific rules for conventional cell representation?

  • The half-cell with the most negative potential goes on the left.
  • The most oxidised species from each half-cell goes next to the salt bridge.
  • A salt bridge is shown using a double line.
  • Always include state symbols.
• What is the standard hydrogen electrode (SHE) used for?

  It is the measuring standard for half-cell potentials

  
• What is the cell potential of the standard hydrogen electrode?

  0.00V
• What are the standard conditions for measuring cell potentials?

  1. 0 moldm^-3 concentration, 298K temperature, 100 kPa pressure
• What materials are used in the standard hydrogen electrode?

  Hydrochloric acid, hydrogen gas, and platinum electrodes
• Why are platinum electrodes used in the standard hydrogen electrode?

  They are metallic and inert, conducting electricity without interfering
• How are cell potentials measured under standard conditions?

  Compared to the standard hydrogen electrode (SHE)
• What does a negative cell potential indicate about a substance?

  It is more easily oxidised and will lose electrons
• What does a positive cell potential indicate about a substance?

  It is more easily reduced and will gain electrons
• How is the overall cell EMF calculated?

  Potential of the right minus the potential of the left

  
• What does a positive overall cell potential indicate about the reaction?

  The reaction is spontaneous and favourable
• What is the anticlockwise rule for combining half-cell reactions?

  1. Write the most negative EMF on top.
  2. Draw anticlockwise arrows around the reactions.
  3. Balance the electrons on both sides.
  4. Write out the cell reaction.
• What type of agents are substances with very positive electrode potentials?

  Better oxidising agents
• What type of agents are substances with very negative electrode potentials?

  Better reducing agents

  
• What effect does increasing the concentration of solutions have on cell EMF?

  It makes the cell EMF more positive
• What effect does increasing the pressure of the cell have on cell EMF?

  It makes the cell EMF more negative
• What are the types of electrochemical cells used for commercial purposes?

  Non-rechargeable, rechargeable, and fuel cells
• What characterizes a rechargeable cell?

  The reaction is reversible, allowing the cell to be reformed
• What type of rechargeable batteries are commonly used in phones and laptops?

  Lithium ion cells
• What electrodes are used in lithium ion cells?

  Lithium Cobalt Oxide and Graphite (Carbon) electrodes

  
• What is the role of the electrolyte in lithium ion cells?

  To carry the flow of charge
• How is a rechargeable cell recharged?

  A current is applied to force electrons to move in the opposite direction
• What distinguishes non-rechargeable cells from rechargeable cells?

  Non-rechargeable cells have irreversible reactions
• What is a fuel cell?

  An electrochemical cell that generates current without needing to be recharged
• What is the most common type of fuel cell?

  The Hydrogen fuel cell
• What does a hydrogen fuel cell use to generate a continuous current?

  A continuous supply of Hydrogen and Oxygen from air

  
• What is the only waste product produced by hydrogen fuel cells?

  Water
• What are the downsides of hydrogen fuel cells?

  High flammability of Hydrogen and expensive production
• Why are hydrogen fuel cells considered environmentally friendly?

  They produce water as the only waste product