RP8 electrochemical cells

• the purpose of a salt bridge is to complete the circuit by allowing ions to move between solutions
• the salt bridge used in an electrochemical cell must not react with the ions in the solution
• electrodes might be rubbed with sandpaper before use to remove the oxide layer which has formed on them
• a specific chemical may not work as part of a salt bridge for the SHE if it would react with the hydrochloric acid and change the concentrations of the ions so change the EMF of the cell
• conditions required for measuring the standard electrode potential are temperature of 298K, pressure of 100kPa and concentration of all solutions of 1.00moldm^-3
• if you are given a solid, to prepare a solution of acidified ions with a known concentration and volume for use in an electrochemical cell you should:

  • work out the number of moles required, use this to work out the mass required
  • measure out the required mass using a balance
  • dissolve in an amount of solvent less than the whole volume
  • transfer the solution to a volumetric flask and make up to the mark
• to set up an electrochemical cell, you should:

  • immerse the electrodes in the solutions
  • connect the solutions by adding a salt bridge
  • connect the electrodes with a voltmeter
• to calculate a standard electrode potential from an electrochemical cell:

  • record the value on the voltmeter, this is the EMF, the E(cell)
  • use the equation E(cell) = E(rhs) - E(lhs)