Chemistry

• What is electrolysis?

  The breaking down of an ionic substance
• What is an electrolyte?

  The solution broken down during electrolysis
• What does oxidation mean?

  The loss of electrons
• What does reduction mean?

  The gain of electrons
• What is the anode?

  The positive electrode
• What is the cathode?

  The negative electrode
• What happens when an ionic compound is melted or dissolved?

  The ions are free to move and conduct electricity
• What is a half equation?

  An equation showing reactions at each electrode
• What happens to negative ions in electrolysis?

  They move to the positive electrode (anode)
• What happens to positive ions in electrolysis?

  They move to the negative electrode (cathode)
• In the electrolysis of lead bromide, which ion goes to the negative electrode?

  Lead (Pb$^{2+}$)
• In the electrolysis of lead bromide, which ion goes to the positive electrode?

  Bromine (Br$^{-1}$)
• What occurs when a positive ion reaches the negative electrode?

  It gains electrons in a reduction reaction
• What occurs when a negative ion reaches the positive electrode?

  It loses electrons in an oxidation reaction
• What do half equations represent?

  The reactions at each electrode and products formed
• What are the products formed during the electrolysis of copper sulphate?

  • Copper (Cu) at the negative electrode
  • Oxygen (O$_2$) and water (H$_2$O) at the positive electrode
• What determines which elements form at each electrode during electrolysis?

  The reactivity of the elements involved
• What ions are present in aqueous copper sulphate?

  Copper (Cu$^{2+}$) and hydrogen (H$^{+}$)
• What is produced at the negative electrode during the electrolysis of brine?

  Hydrogen gas (H$_2$)
• What is produced at the positive electrode during the electrolysis of brine?

  Chlorine gas (Cl$_2$)
• What is the role of cryolite in extracting aluminium?

  It reduces the melting point of aluminium oxide
• What are the gas tests for identifying gases?

  • Hydrogen: Squeaky pop with lit splint
  • Oxygen: Glowing splint relights
  • Chlorine: Bleaches damp litmus paper
  • Carbon dioxide: Limewater turns cloudy
• What is formed at the negative electrode during aluminium extraction?

  Aluminium atoms (Al)
• What is formed at the positive electrode during aluminium extraction?

  Oxygen gas (O$_2$)
• What happens to oxygen produced at the positive electrode?

  It reacts with carbon to form carbon dioxide
• What is the half equation for aluminium at the negative electrode?

  Al$^{3+} +$$3e^{-} \rightarrow Al$
• What is the half equation for oxygen at the positive electrode?

  2O$^{2-} \rightarrow O<latex>_2$ + 4e^{-}
• What happens during the electrolysis of brine?

  • Sodium chloride solution is electrolyzed
  • Hydrogen gas (H$_2$) at negative electrode
  • Chlorine gas (Cl$_2$) at positive electrode
  • Sodium hydroxide (NaOH) remains in solution