ELECTROLYSIS

• What is investigated in the electrolysis of aqueous solutions?

  The products of electrolysing different solutions
• What are the products of electrolysing potassium iodide solution?

  Hydrogen and iodine
• What is the product at the cathode during electrolysis of potassium iodide?

  Hydrogen
• What is the product at the anode during electrolysis of potassium iodide?

  Iodine
• What does the half equation K+ + e- → K represent?

  Reduction of potassium ions
• What is the product discharged at the negative electrode when electrolysing silver nitrate solution?

  Silver

  
• What is the product discharged at the positive electrode when electrolysing silver nitrate solution?

  Oxygen
• Why should measuring cylinders be used instead of test tubes in gas volume measurement?

  Test tubes cannot measure volume accurately
• What indicator can show the presence of sodium hydroxide?

  Universal indicator
• What color does universal indicator turn in sodium hydroxide solution?

  Blue or purple
• How would you test the hypothesis that the product at the negative electrode is always a metal?

  • Use different salt solutions
  • Observe for solid metal deposit at the negative electrode
• Why is the student's hypothesis about the negative electrode only partially correct?

  Sometimes hydrogen is produced instead
• What test is used to identify chlorine gas?

  Damp litmus paper turns white
• What happens to litmus paper when exposed to chlorine gas?

  It is bleached and turns white
• What is the test for oxygen gas?

  A burning splint makes a pop sound
• What happens to a glowing splint in oxygen gas?

  The splint relights
• What is the test for hydrogen gas?

  A burning splint makes a pop sound
• Why is hydrogen produced at the negative electrode instead of sodium?

  Hydrogen is less reactive than sodium
• Why do hydrogen ions move to the negative electrode?

  Because they are positively charged
• How does a hydrogen ion change into a hydrogen atom?

  It gains an electron
• What is produced at the positive electrode during electrolysis of sodium chloride solution?

  Chlorine gas

  
• What is produced at the negative electrode during electrolysis of sodium chloride solution?

  Hydrogen gas

  
• What happens to hydrogen ions at the negative electrode?

  They gain electrons to form hydrogen gas
• What are the observations when a current is passed through different salt solutions during electrolysis?

  • Copper chloride: chlorine bubbles, copper deposit
  • Copper sulfate: oxygen bubbles, copper deposit
  • Sodium chloride: chlorine bubbles, hydrogen bubbles
  • Sodium sulfate: oxygen bubbles, hydrogen bubbles
• What is the reactivity series of metals from most to least reactive?

  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Magnesium
  • Aluminium
  • Carbon
  • Zinc
  • Iron
  • Hydrogen
  • Copper
  • Gold
• What happens to copper ions during electrolysis?

  They move to the positive electrode

  
• What is the role of the power supply in electrolysis?

  It provides the electric current
• What is the purpose of using inert electrodes in electrolysis?

  They do not react with the electrolyte
• What is the significance of using a low voltage power supply?

  It prevents excessive heat generation
• What is the effect of increasing the concentration of copper sulfate on copper deposition?

  More copper is deposited
• What is the role of the litmus paper in identifying chlorine gas?

  It indicates bleaching when exposed
• What happens to the electrodes during electrolysis?

  They may become coated with products
• What is the importance of safety precautions during electrolysis?

  To prevent inhalation of harmful gases
• What is the purpose of using a petri dish lid during electrolysis?

  To prevent evaporation of the solution
• What is the significance of the observation at the anode during electrolysis?

  It indicates the type of gas produced
• What is the effect of using different salt solutions in electrolysis?

  It changes the products at the electrodes
• What is the relationship between ion charge and electrode attraction?

  Opposite charges attract each other
• What is the role of hydroxide ions in electrolysis?

  They participate in oxidation reactions
• What is the significance of the reactivity series in electrolysis?

  It determines which ions are discharged
• What is the effect of time on gas volume during electrolysis?

  Gas volume increases with time