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Junction Potential quiz

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  • What is a junction potential in electrochemistry?
    A junction potential is the voltage that develops at the interface between two ionic solutions due to differences in ion mobility and concentration.
  • What role does the salt bridge play in an electrochemical cell?
    The salt bridge allows ions to move and counterbalance electron flow, completing the circuit and helping to minimize junction potential.
  • Why do ions move from one side of a semi-permeable membrane to the other?
    Ions move from areas of higher concentration to lower concentration to achieve equilibrium.
  • How does ion size affect ion mobility across a membrane?
    Smaller ions move faster than larger ions, leading to differences in how quickly they cross the membrane.
  • Why does a build-up of charge occur on either side of a semi-permeable membrane?
    Because ions with different mobilities cross at different rates, leading to an accumulation of positive or negative charge on each side.
  • Which ion moves faster: H+ or Br-? Why?
    H+ moves faster than Br- because it is smaller in size.
  • What happens to the right side of the membrane when H+ moves faster than Br-?
    The right side becomes more positively charged due to the faster accumulation of H+ ions.
  • What is the effect of using ions with similar mobility in a salt bridge?
    Using ions with similar mobility minimizes the junction potential, making it nearly negligible.
  • Why is potassium chloride (KCl) commonly used in salt bridges?
    KCl is used because K+ and Cl- have similar mobilities, resulting in a very small junction potential.
  • How is the overall cell potential (Ecell) calculated?
    Ecell is calculated as the potential of the cathode minus the potential of the anode.
  • Why is it important to consider junction potential in electrochemical measurements?
    Junction potential can affect the accuracy of cell potential measurements if not minimized or accounted for.
  • What two main factors influence the magnitude of the junction potential?
    The concentration of the solutions and the differences in ion mobility influence the junction potential.
  • What happens if the ions in the salt bridge have very different mobilities?
    A significant junction potential develops, which can interfere with accurate cell potential measurements.
  • What is the typical mobility value for H+ compared to Br-?
    H+ has a mobility of 36.30 × 10⁻⁸, while Br- has a mobility of 8.13 × 10⁻⁸, making H+ much faster.
  • How can you minimize the junction potential in an electrochemical cell?
    By using a salt bridge with ions of similar size and mobility, such as KCl, the junction potential is minimized.