The periodic table is made up of two main sections; the groups and the transition metals. The transition metals area group of elements that can have variable oxidation states and two of these metals are going to be studied into more detail.
Properties
Transition elements have got a number of different properties than normal elements:
- They form coloured compounds.
- They can have different valencies.
- Due to the fact that these compounds can possess different valencies they can be used as catalysts.
Iron
Iron can have two main oxidation states, the II and the III. The most stable oxidation state is the III and Fe2+ can be easily oxidized to Fe3+, especially if left in the air.
The three main reactions for iron are its combustion, reaction with steam, hydrogen chloride and chlorine.
Combustion
Altough Iron can react with Oxygen to produce both FeO and Fe2O3 none of these compounds are formed, and instead the compound Fe3O4 would be formed, which is a mixed oxide. Rust, Fe2O3.xH2O can be formed by the reaction of Iron with oxygen in the presence of water.
3Fe + 2O2 → Fe3O4
Steam
Iron can be reacted with steam to displace the Hydrogen, producing the oxide and Hydrogen. The oxide can be both the mixed oxide or that for Fe3+, although the Fe3+ is normally produced. If excess steam and higher temperatures are used the mixed oxide would form.
3Fe + 4H2O → Fe3O4 + 4H2
Hydrogen Chloride
The reaction of Iron with Hydrogen Chloride would yield Iron (II) Chloride, which is green in colour.
Fe + 2HCl → FeCl2 + H2
Chlorine
While Iron (II) is produced with HCl Iron (III) would be produced with Cl2, mainly due to the fact that Chlorine is a much better oxidizing agent then Hydrogen.
2Fe + 3Cl2 → 2FeCl3
Copper
Copper (II) Oxide
CuO is a black solid. This can be used to prepare Copper (II) salts by reacting with acids:
CuO + H2SO4 → CuSO4 + H2O
CuO + 2HCl → CuCl2 + H2O
Preparation of Copper (II) Oxide
Copper (II) Oxide can be prepared by the decomposition of copper (II) carbonate and copper (II) nitrate.
CuCO3 → CuO + CO2
Cu(NO3)2 → CuO + 2NO2 0.5O2
Reduction of Copper (II) Oxide by Hydrogen
As hydrogen is higher up in the reactivity series than Copper, hydrogen will displace copper, producing copper and water.
CuO + H2 → Cu + H2O