Chemical Changes

• What do metals produce when they react with oxygen?

  Metal oxides
• What type of reaction occurs when metals react with oxygen?

  Oxidation reactions
• What is oxidation in terms of electrons and oxygen?

  Loss of electrons, gain of oxygen
• What is reduction in terms of electrons and oxygen?

  Gain of electrons, loss of oxygen
• How is the reactivity of a metal related to its tendency to form positive ions?

  More reactive metals lose electrons more readily
• What is the order of metals in the reactivity series from most to least reactive?

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminium
  • Zinc
  • Iron
  • Tin
  • Lead
  • Hydrogen
  • Copper
  • Silver
  • Gold
• How are metals above carbon extracted from their ores?

  Using electrolysis
• What happens to metals above carbon during electrolysis?

  They form H₂ gas
• What happens to metals below carbon during electrolysis?

  They form solid metals
• What can a more reactive metal do to a less reactive metal?

  Displace it from a compound
• Where are unreactive metals like gold found?

  As the metal itself in the earth
• How can metals less reactive than carbon be extracted?

  By reduction with carbon
• What is the general reaction of metals with acids?

  Metal + Acid → Salt + Hydrogen
• Why is the reaction of metals with acids considered a redox reaction?

  Because metals give electrons to hydrogen ions
• What are the neutralization reactions involving acids?

  1. Acid + Alkali → Salt + Water
  2. Acid + Metal → Salt + Water
  3. Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
• What do bases include in the context of neutralization reactions?

  Metal oxides and metal hydroxides
• What determines the salt produced in a neutralization reaction?

  The acid used and positive ion in the base
• How can soluble salts be made in neutralization reactions?

  By filtering excess and evaporating the solution
• What are the steps to prepare a pure, dry sample of a soluble salt from an insoluble oxide or carbonate?

  1. Measure dilute acid and warm gently.
  2. Add excess base until no more reacts.
  3. Filter out excess base.
  4. Evaporate remaining solution to crystallize.
  5. Leave salt to dry.
• What happens to the pH of the mixture during the neutralization process?

  It gradually increases, then steeply increases
• What is the pH scale range?

  0 to 14
• What do acids produce in aqueous solutions?

  Hydrogen ions (H⁺)
• What do alkaline solutions contain?

  Hydroxide ions (OH⁻)
• What is the pH of a neutral solution?


  7
• What happens in neutralization reactions between an acid and an alkali?

  H⁺ reacts with OH⁻ to produce water
• What is an example of a strong acid?

  HCl
• What is an example of a weak acid?

  CH₃COOH
• How is the pH scale related to the concentration of H⁺ in a solution?

  Concentration increases, pH decreases
• What happens to the pH when the concentration decreases by a factor of 10?

  pH goes up by one unit
• What is the process of titration used for?

  • Measuring volumes of acid and alkali
  • Using an indicator to determine endpoint
• What are the steps in the titration practical?

  1. Pipette base into conical flask.
  2. Add methyl orange indicator.
  3. Wash and fill burette with acid.
  4. Add acid to base until color change.
  5. Record volume for rough titration.
  6. Repeat for concordant results.
• What is the formula for calculating moles?

  mol = volume × concentration / 1000
• How do you find missing values in titration calculations?

  Use balanced equation ratio
• What is electrolysis used for in metal extraction?

  To break down ionic compounds
• What happens to ions during electrolysis?

  They are attracted to electrodes of opposite charge
• What is produced at the cathode during electrolysis of molten ionic compounds?

  Metal
• What is produced at the anode during electrolysis of molten ionic compounds?

  Non-metal
• What is produced at the cathode during electrolysis of aqueous solutions if the metal is more reactive than hydrogen?

  Hydrogen gas
• What is produced at the anode during electrolysis of aqueous solutions if there is a halide ion?

  Halogen
• What is the half equation for oxidation of O²⁻ ions?

  4O²⁻ → 2O₂ + 4e⁻