Chem unit 2

• How is a metal Malleable and Ductile?

  Malleable= Can be hammered into shape

  Ductile= Can be stretched into wires
• Why do metals have high boiling points?

  Due to strong forces of attraction between positive protons and negative electrons
• Why is a metal a good conductor of electricity?

  Delocalised electrons are free to move and carry charge
• How is a metal a good conductor of heat?

  Positive ions are packed closely together so heat energy can be passed from one particle to another.
• How can metals with high reactivity be extracted from their ores?

  By a process called electrolysis
• How can metals with medium reactivity be extracted from their ores?

  By displacement by heating the metal oxide with carbon
• Carbon can be used to extract a metal from its ore


  only when it is higher in the reactivity series than the metal being extracted.
• Displacement reaction


  When a more reactive element takes the place of a less reactive element in a compound.
• Does Copper react with HCl

  No. Copper does not react with HCl, since if a metal is less reactive than hydrogen, it will not react with the acid.
• Does Magnesium react with HCl

  Yes. Products formed will be Magnesium Chloride and Hydrogen. This is because if a metal is more reactive than hydrogen, it will displace hydrogen from the acid.
• Complete the balanced symbol equation aluminium + iron oxide-->

  2Al + Fe2O3 -->


  Aluminium oxide + Iron

  Al2O3 + 2Fe
• Complete the equation zinc and sodium nitrate

  Zinc and sodium nitrate will remain unchanged since Zinc is less reactive than sodium and can't displace sodium from its compound
• Zinc can displace Copper from Copper sulphate and Iron from Iron sulphate but not Magnesium from Magnesium sulphate. And Iron can displace copper from copper sulphate. Put the metals in order of reactivity.


  Magnesium>Zinc>Iron>Copper
• Iron can be produced from a mixture of aluminium and iron oxide but not from a mixture of copper and iron oxide. Write the name of the metals in order of reactivity


  Aluminium, Iron, Copper
• Name two unreactive metals?

  Silver and Gold
• Reduction


  removal of oxygen atoms from a compound or gain of electrons
• Oxidation


  Addition of oxygen atoms to an element or compound or the loss of electrons
• Electrolysis


  Splitting of a compound into its elements using electricity
• In electrolysis, why should the aluminium oxide be molten or why should the ionic compound be in solution


  When molten or in solution, ions are free to move.
• In the electrolysis of what water, what is the electrolyte?

  Water
• Electrolyte


  a compound that conducts an electric current when it is in an aqueous solution or in the molten state
• Three advantages to recycling Aluminium

  Uses only 5% of the energy needed to extract new aluminium from bauxite using electrolysis.

  cuts down on waste sent to landfill

  saves natural resources.
• What does the term PANIC help you remember

  Positive Anode, Negative is Cathode
• Cathode


  Is the negative electrode and attracts positive metal ions (called cations). This is where reduction takes place and electrons are gained.
• Anode


  Is the positive electrode and attracts negative non metal ions (called anions). This is where oxidation takes place and electrons are lost.
• What does OiLRiG mean?

  Oxidation is the Loss of electrons; Reduction is the Gain of elctrons
• Four raw materials for the extraction of iron and their purpose

  Limestone: removes impurities and forms molten slag

  Iron ore (Fe2O3) is a source of iron

  Hot air provides oxygen

  Coke is a form of carbon which acts as a fuel and reacts with oxygen to form Carbon monoxide which is then used to reduce the Iron oxide.
• Describe the extraction of Iron?

  1. Combustion: Coke reacts with hot air

  C + O2 --> CO2

  Then CO2 + C --> 2CO

  2.Reduction

  Iron (III) oxide in ore is reduced to form molten iron. The Carbon monoxide acts as the reducing agent and gets oxidised by gaining the oxygen from the Iron oxide to form carbon dioxide.

  Fe2O3 + 3CO --> 2Fe + 3CO2

  3.Thermal Decomposition of Limestone at high temp in furnace

  CaCO3 --> CaO + CO2

  3. Neutralisation

  CaO + SiO2 --> CaSiO3 (which is molten slag) which is then used to make roads

  Note that the molten iron is always collected below the molten slag.
• What is an ore?


  Substance found in the Earth's crust containing metal atoms
• How is Aluminium extracted?

  By electrolysis
• What happens during the extraction of aluminium?

  Aluminium oxide is heated to high temperatures making it melt. Cryolite is used to lower the melting point.

  Aluminium ions being positively charged move towards the negatively charged cathode where reduction takes place (electrons are gained) to form Aluminium metal. (silvery grey solid seen at the cathode)

  
  

  Al3+ + 3e- --> Al

  
  

  The Oxide ions (O2-) being negatively charged moved towards the positively charged anode where oxidation takes place (electrons are lost) to form oxygen gas. (bubbles are seen at the anode).

  
  

  2O2- --> O2 + 4e-
• What are the issues with the extraction of metals from their ores?

  Fuel and energy costs

  Greenhouse gas emissions

  Impact of recycling
• Electrolysis of Lead Bromide (PbBr2)

  At cathode: silvery grey solid Lead forms

  This is because positively charged Pb2+ ions are attracted to negatively charged electrode.

  Pb2+ + 2e- --> Pb

  At Anode: orange brown liquid of Br2 forms.

  This is because negatively charged Br- ions are attracted to the positively charged electrode.

  2Br- --> Br2 + 2e-
• Electrolysis of water


  At cathode: The H+ ions are attracted to negatively charged electrode. Reduction takes place and H+ ions gain electrons to form Hydrogen gas.

  2H+ + 2e- --> H2

  At Anode: The OH- ions are attracted to the positive anode where they are oxidised by losing electrons.

  2OH- --> O2 + 2H+ + 4e-

  Note the volume of Hydrogen formed is twice that of oxygen since in each molecule of water, there are two H atoms and one atom of oxygen.
• Electrolysis of copper sulphate using graphite electrodes


  At cathode: copper is formed (seen as a reddish brown deposit)

  Cu2+ ions are attracted to negative cathode where reduction takes place.

  Cu2+ + 2e- -->Cu

  At anode: Oxygen gas is formed (bubbles are seen)

  O2- ions are attracted to positive anode where oxidation takes place.
• Electrolysis of copper sulphate using copper electrodes

  At cathode: copper is formed (seen as a reddish brown deposit). Eventually the cathode gets bigger.

  Cu2+ ions are attracted to negative cathode where reduction takes place.

  Cu2+ + 2e- -->Cu

  At anode: (eventually you will see that the copper anode gets smaller.

  Anode is made of impure copper metal

  The copper in the positive electrode is oxidised to generate Cu2+ ions.

  Cu --> Cu2+ + 2e-

  Impurities collect as the bottom as sludge

  The Cu2+ concentration stays the same, since the Cu2+ ions leave and enter at the same rate. This is why the solution remains blue
• What is Electroplating and when can it be used?

  Uses: Purification of copper and manufacture of sodium hydroxide.

  This uses the electrolysis process.

  The object being plated must be the cathode so that the metal can be deposited on it.

  The electrolyte must contain the ions of the metal that will be used to coat the object.

  Positive metal ions are attracted to the cathode and they gain electrons to neutralise their positive charge and form the metal.

  E.g Silver ions Ag+ in silver nitrate solution will be attracted to the cathode to deposit on a piece of cutlery as silver metal.

  Ag+ + e- --> Ag
• Electrolysis of copper chloride

  At cathode: copper is formed (seen as a reddish brown deposit)

  Cu2+ ions are attracted to negative cathode where reduction takes place.

  Cu2+ + 2e- -->Cu

  At anode: Chlorine gas is formed (bubbles are seen)

  Cl- ions are attracted to positive anode where oxidation takes place.

  2Cl- --> Cl2 + 2e-
• Electrolysis of Sodium chloride

  The electrolyte is sodium chloride solution and contains Na+, Cl-, H+ and OH- ions are present.

  At cathode: Hydrogen gas is formed (seen as bubbles)

  This is because if the metal is higher in the reactivity series than hydrogen then hydrogen is formed at the cathode.

  2H+ + 2e- --> H2

  At anode: Chlorine gas is formed (bubbles are seen)

  Cl- ions are attracted to positive anode where oxidation takes place.

  2Cl- --> Cl2 + 2e-

  The Na+ and OH- ions are left in the solution and form sodium hydroxide.
• Uses of Hydrogen, chlorine and Sodium Hydroxide produced during the electrolysis of sodium chloride solution (Brine)


  Hydrogen used as a fuel

  Chlorine used to make bleach and plastics)

  Sodium Hydroxide used to make soap