C4-Chemical changes

• What do alkalis form in water?

  OH⁻ ions
• What is the pH range of acids?

  pH 0 to 6
• What are the products of neutralisation reactions?


  Salt and water
• What is the neutral pH value?

  pH 7
• What is the general equation for neutralisation reactions?

  acid + base → salt + water
• What does a universal indicator do?

  It changes colour depending on the pH
• What is the advantage of using a pH probe?

  It gives an accurate value of the pH
• How do you obtain the formula of a salt?

  Balance the charges of the ions
• What is produced when an acid reacts with a metal oxide?

  Salt and water
• What is produced when an acid reacts with a metal carbonate?

  Salt, water, and carbon dioxide
• What is produced when an acid reacts with a metal hydroxide?

  Salt and water
• What salt is produced from hydrochloric acid (HCl)?

  Chloride
• What salt is produced from sulfuric acid (H₂SO₄)?

  Sulfate
• What salt is produced from nitric acid (HNO₃)?

  Nitrate
• How are soluble salts made from acids?

  Add metals or insoluble metal compounds to acids
• What happens to the excess solid when making soluble salts?

  It is filtered off
• What is the first part of a salt's name derived from?

  The positive ion in the base, alkali, or carbonate
• What is the reactivity series?

  A list of metals arranged by their ability to form positive ions
• Which metal is the most reactive in the reactivity series?

  Potassium
• Which metal is the least reactive in the reactivity series?

  Gold
• What happens during oxidation of a metal?

  It gains oxygen
• What happens during reduction of a metal?

  It loses oxygen
• What is produced when a metal reacts with an acid?

  Salt and hydrogen
• What is a displacement reaction?

  When a more reactive element displaces a less reactive metal from its compound
• How does the reactivity of metals affect hydrogen production?

  The more reactive the metal, the faster hydrogen bubbles are produced
• What happens to negative non-metal ions during electrolysis?

  They move towards the anode
• What is an electrolyte?

  A liquid or solution that can conduct electricity because ions are free to move
• What happens to positive metal ions during electrolysis?

  They move towards the cathode
• What is produced at the cathode during electrolysis of aqueous ionic compounds if the metal is less reactive than hydrogen?

  The metal
• What is produced at the anode during electrolysis of aqueous ionic compounds if no halide ions are present?

  Oxygen gas and hydrogen ions
• What is produced at the anode during electrolysis of aqueous ionic compounds if halide ions are present?

  A halogen
• What is the purpose of cryolite in the extraction of aluminium?

  To lower the melting point
• Why does extracting metals via electrolysis require a lot of energy?

  Because it involves breaking strong ionic bonds
• What are the main reactions of acids with metals and their products?

  • Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
  • Acid + Metal Oxide → Salt + Water
  • Acid + Metal Hydroxide → Salt + Water
• What are the steps involved in the electrolysis of molten ionic compounds?

  1. Flow of electrons occurs.
  2. Positive metal ions move towards the cathode.
  3. Negative non-metal ions move towards the anode.
  4. Metal is extracted at the cathode.
• What are the steps involved in the electrolysis of aqueous ionic compounds?

  1. Metal produced at cathode if less reactive than H₂.
  2. H₂ produced at cathode if metal is more reactive than H₂.
  3. Halogen produced at anode if halide ions are present.
  4. O₂ produced at anode if no halide ions are present.
• What are the key points about the reactivity of metals?

  • Metals are arranged in the reactivity series.
  • More reactive metals easily form positive ions.
  • Less reactive metals do not easily form positive ions.
• What are the key points about oxidation and reduction in metals?

  • Oxidation: Gain of oxygen.
  • Reduction: Loss of oxygen.
• What are the strengths and weaknesses of using electrolysis for metal extraction?

  Strengths:

  • Effective for extracting reactive metals.
  • Can purify metals.

  
  

  Weaknesses:

  • Requires a lot of energy.
  • Expensive process.
• What are the products of neutralisation reactions?

  • Salt
  • Water