Chemistry: Exam Topics

Chemistry: Exam Topics

1. Acids and Metals

   • Different metals will have different reactions when mixed with an acid. For example: When Zinc reacts with Hydrochloric acid it will the salt Zinc Chloride and Hydrogen.
   • When comparing magnesium, zinc, iron and lead in dilute hydrochloric acid, magnesium reacts the most vigorously, this is because it is nearerest to thr top of the reactivity series. Next, zinc and iron will react similarly and bubble more steadily in the dilute acid. Whereas lead has a much slower reaction - due to it being situated nearer to the bottom of the reactivity series.
     • magnesium (s) + oxygen (g) → magnesium oxide (s)

2. Metals and Water

   • When metals react with water they react to produce a metal hydroxide and hydrogen or a metal oxide and hydrogen.
     • calcium + water → calcium hydroxide + hydrogen
       • Calcium bubbles vigorously when it comes in contact with water, then it seems to just... Disappear! The bubbles formed is one of the products of the reaction: it's hydrogen gas.
   • All Group 1 metals react with water to produce hydrogen and a soluble hydroxide. When potassium reacts with water it reacts vigorously and produces a flame. Although Sodium and Lithium react slightly less vigorously.
   • Whereas metals such as: Copper or Gold don't react at all with water or steam, just as they don't react with dilute acids or oxygen. Making them perfect for their uses as copper pipes and gold jewellery.
   • Metals will also react with steam. When magnesium reacts with cold water it has a slow reaction, whereas when combined with steam magnesium has a much faster reaction. Zinc and iron also react with steam, (but not water) to produce a metal oxide and hydrogen.
     • (STEAM:) magnesium + water → magnesium oxide + hydrogen = Mg (s) + H²O (g) → MgO (s) + H² (g)

3. Extracting Metals

   • Displacement Reactions
     • Carbon is more reactive than copper, therefore carbon would be able to displace it from the compound copper oxide. (Similarly to how magnesium or iron can displace copper from the compound, copper sulfate.) Any metal that is after carbon in the reactivity series, will be displaced from its compound by carbon.
       • carbon + copper oxide → copper + carbon dioxide = C (s) + 2CuO (s) → CO² (g)
         • Symbol for Lead = Pb
   • A rock that you can extract a metal from is called an ore. Therefore, Iron ore would be a mixture of iron oxide and various other compounds. Just as, Aluminium ore is a mixture of aluminium oxide and other compounds.
     • To extract a metal from its ore: 1. You first, seperate the metal oxide from the compounds it's mixed with. 2. Then you'd use chemical reactions (these chemical reactions involve heating the metal oxide with charcoal - a form of carbon that is cheap) to extract the metal from the metal oxide.

4. Metals and Oxygen

   • When a metal is burnt it will react with oxygen from the air and produce a metal oxide. Various metals will have different reaction with the oxygen, and some react more vigorously than others.
   • Magnesium: burns vigorously in oxygen. Zinc: burns less vigorously in oxygen. Iron: burns in oxygen. Lead and Copper: does not burn, when heated, forms a layer of oxide on a surface. Gold: no reaction
     • Magnesium reacts quite vigorously with oxygen in the air because it is nearer to the top of the reactivity series (it is 4th from the top). 
     • Gold has no reaction with oxygen because it is at the bottom of the reactivity series.
     • STATE SYMBOLS - zinc + oxygen → zinc oxide = 2Zn (s) + O² (g) → 2ZnO (s)
       • (s) - Solid, (g) - Gas, (l) - Liquid, (aq) - Aqueous/Dissolved in Water
   • For example: When magnesium is burnt, it reacts with oxygen from the air vigorously and produces magnesium oxide. However magnesium doesn't have to be heated to react with oxygen

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