topic 4

• Metal is produced at the cathode if it is less reactive than hydrogen
• Hydrogen is produced at the cathode if the metal is more reactive than hydrogen
• Oxygen is produced at the anode unless halide ions are present.

  In that case, the negatively charged halide ions lose electrons and form the corresponding halogen
• What does electrolysis mean?

  'Splitting Up with Electricity'
• What is the role of an electrolyte in electrolysis?

  It conducts electricity and contains ions
• What happens to positive ions during electrolysis?

  They move towards the cathode and gain electrons
• What happens to negative ions during electrolysis?

  They move towards the anode and lose electrons
• What is an electrode?

  A solid that conducts electricity
• What does it mean when ions are discharged?

  They don't have a charge
• Why can't an ionic solid be electrolyzed?

  Because ions can't move freely
• What happens to molten positive metal ions during electrolysis?

  They are reduced to the element at the cathode
• What is the purpose of mixing aluminium oxide with cryolite?

  To lower the melting point
• What do positive Al ions do at the negative electrode?

  They gain three electrons and become neutral
• What do negative O ions do at the positive electrode?

  They lose two electrons
• What is produced at the negative electrode during electrolysis?

  Aluminium
• What is produced at the positive electrode during electrolysis?

  Oxygen
• What is the overall equation for the electrolysis of aluminium oxide?

  Aluminium oxide → Aluminium + Oxygen
• Why is the carbon anode replaced regularly?

  It reacts with oxygen to produce carbon dioxide
• What is the reactivity series?

  Order of metals based on reactivity
• How is a metal's reactivity determined?

  By how easily it loses electrons
• What happens when metals react with water or acid?

  They lose electrons and form positive ions
• What is the general reaction of a metal with an acid?

  Acid + Metal → Salt + Hydrogen
• How does the speed of reaction relate to metal reactivity?

  More reactive metals react faster
• What is the reaction of magnesium with dilute hydrochloric acid?

  Mg + 2HCl → MgCl₂ + H₂
• What is the reaction of zinc with dilute hydrochloric acid?

  Zn + 2HCl → ZnCl₂ + H₂
• What is the reaction of iron with dilute hydrochloric acid?

  Fe + 2HCl → FeCl₂ + H₂
• How can the reactivity of metals be investigated?

  By measuring temperature change during reactions
• What do metals produce when they react with water?

  Metal Hydroxide + Hydrogen
• Which metals react with water?

  Potassium, sodium, lithium, calcium
• What is the difference between strong and weak acids?

  Strong acids ionize completely, weak acids do not
• What do strong acids produce in water?

  Hydrogen ions (H⁺)
• What is the ionization of a weak acid?

  It is a reversible reaction
• How does pH relate to hydrogen ion concentration?

  Lower pH means higher H⁺ concentration
• What happens to H⁺ concentration when pH decreases by 1?

  It increases by a factor of 10
• What is the factor change in H⁺ concentration for a pH decrease of 2?

  It increases by a factor of 100
• What is the general rule for H⁺ ion concentration changes?

  Factor H⁺ ion concentration changes by = 10⁻⁽difference in pH⁾
• How does acid strength differ from acid concentration?

  Strength refers to ionization proportion, concentration to amount
• How does the concentration of H⁺ ions affect the rate of reaction?

  Higher H⁺ concentration leads to faster reactions
• What is more reactive, strong acids or weak acids of the same concentration?

  Strong acids are more reactive
• What does pH measure in a solution?

  The concentration of H⁺ ions