Chemical Changes (Acid & bases and salts, Electrolysis and Reacitivty of metals)

• What forms when oxygen reacts with a metal?

  Metal oxide
• What is a redox reaction?

  Oxidation and reduction involve the addition or removal of oxygen from a substance
• What happens to oxygen in oxidation?

  Oxygen is added to an element or compound
• What happens to oxygen in reduction?

  Oxygen is removed from an element or a compound
• Why are carbon and hydrogen useful?

  As they can extract metals from their oxide by reduction
• Reactivity series Mnemonic table

  Most reactive:

  Potassium - Please

  Sodium - Send

  Lithium - Lions

  Calcium - cats

  Magnesium - Monkeys

  Aluminium - And

  Carbon - Cute

  Zinc - Zebras

  Iron - Into

  Hydrogen - Hot

  Copper - Countries

  Silver - Signed

  Gold - Gordon
• What metals in the reactivity series will react with water?

  Metals above hydrogen
• Equation for metal that reacts with water

  Metal + water -> metal hydroxide + hydrogen
• Which metals will react with acids in the reactivity series?

  The ones below hydrogen
• Equation for metals and acid reacting

  Metal + acid -> metal salt + hydrogen
• What is carbon and what is it used for in the reactivity series?

  Carbon is a cheap reducing agent and can be used to remove oxygen for metal oxide ores
• Which metals can be extracted by heating the oxide with carbon?

  The metals below carbon
• How do the metals higher than carbon get extracted?

  Electrolysis
• Why can one metal displace another?

  The more reactive metal will displace a less reactive metal from its compound
• Two examples of this

  -Reacting a metal with a metal oxide (by heating)

  -Reacting a metal with an aqueous solution of a metal compound
• How can you tell in displacement reactions between metals & aqueous solution of metal salts

  The more reactive metal slowly disappears from the solution, displacing the less reactive metal
• How can a metal be extracted from its ore?

  Electrolysis, using a blast furnace or by reacting with a more reactive material
• Metals higher up in the reactivity series are __________ to oxidation

  Less resistant
• Metal lower down in the reactivity series are ___________ to oxidation

  More resistant
• Equation for metal oxide + carbon

  Metal oxide + carbon -> metal + carbon dioxide
• Which metals in the reactivity series will react with dilute acids?

  Only metals above hydrogen
• How will the reaction be when the metal is more reactive?

  More vigorous
• Equation for metal + acid

  metal + acid --> salt + hydrogen
• What are metal-acid reactions?

  Redox reactions
• Equation between zinc and hydrochloric acid

  Zn + 2HCL -> ZnCl2 + H2
• Ionic equation for this


  Zn + 2H+ -> Zn2+ + H2
• What happens when an acid reacts with a base>

  A neutralisation reaction occurs
• What are bases ph value?

  Above 7
• What are most bases?

  Insoluble
• But if they do dissolve in water what are they called?

  Alkalis
• What does this form?

  Alkaline solution
• What is produced in an acid-base neutralisation reaction?

  Acid + base -> salt + water
• What would the equation be if the base is a metal carbonate?

  Acid + base -> salt + water + carbon dioxide
• What are different types of bases?

  Metal oxides, metal hydroxides, metal carbonates
• How is a soluble salt made?

  From the reaction of an acid with an insoluble base
• What is added in excess to ensure all of the acid has reacted?

  The insoluble reactant
• What happens if this step is not completed?

  Any unreactive acid would become dangerously concentrated during evaporation and crystallisation
• How is a the excess reactant removed?

  By filtration to ensure that only the salt and water remain
• Diagram of this practical

  
• Method for this practical

  1) Add 50 cm3 dilute acid into a beaker and warm gently using a Bunsen Burner

  2) Add the insoluble oxide slowly to the hot dilute acid and stir until the base is in excess (until the base stops dissolving and a suspension of the base forms in the acid)

  3) Filter the mixture into an evaporating basin to remove the excess base

  4) Gently heat the solution in a water bath or with an electric heater to evaporate the water until at crystallisation point

  5) Check the solution is at crystallisation point by dipping a cold glass rod into the solution and see if crystals form on the end

  6) Leave the filtrate in a warm place to dry and crystallise

  7) Allow crystals to dry