Electrolysis

Electrolysis

1. What is Electrolysis?

   • The decomposition of a compound using electrical energy
   • The electricity used comes from a d.c source, such as a battery
   • It requires liquid to conduct the electricity, called the electrolyte
   • The electricity is applied to the electrolyte by two electrodes
   • The electrolyte contains the compound, which is broken down into its component parts
   • The component parts are released as atoms or molecules - often as a gas

2. Electrolysing Hydrochloric Acid

   • The electrolyte is a dilute solution of hydrochloric acid
   • Applying a d.c current to the electrolyte causes the hydrochloric acid to decompose into two component parts
     • Hydrogen
       • You can test for this as it makes a "squeaky-pop" with a lighted splint.
       • H2 is positive and so it's attracted to the cathode
     • Chlorine
       • You can test for this as chlorine bleaches damp litmus paper, turning it white. Or red for a moment at first as chlorine is acidic.
       • Cl2 is negative and so it's attracted to the anode
   • The gases bubble through the solution and can be collected at the electrodes

3. Electrodes

   • Anode
     • has a positive charge
     • attracts anions (negative ions)
     • oxidation - reduction loss
   • Cathode
     • has a negative charge
     • attracts cations (positive ions)
     • reduction - electron gain

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