Group 4

Cards (60)

  • Group IV tetrachlorides

    All the elements in Group IV form tetrachlorides, XCI4
  • Tetrachlorides
    • Simple covalent molecules with tetrahedral structure
    • Volatile liquids with low boiling points
    • Non-polar because the dipoles cancel
  • There is no simple pattern in the boiling points of the tetrachlorides
  • Group IV tetrachlorides

    Compounds formed by Group IV elements (C, Si, Ge, Sn, Pb) with four halogen atoms
  • Reactivity of the Group IV tetrachlorides with water

    1. All the tetrahalides, except CCl4, are readily hydrolysed by water to the oxide in the +4 oxidation state
    2. Acidic fumes of hydrogen chloride are also produced
  • Hydrolysis reaction of tetrachlorides

    • SiCl4(l) + 2H2O(l) → SiO2(s) + 4HCl(g)
    • GeCl4(l) + 2H2O(l) ⇌ GeO2(s) + 4HCl(g)
  • Hydrolysis of the Group IV tetrachlorides
    • The hydrolysis is reversible for the heavier tetrachlorides
    • The case of hydrolysis increases down the group from SiCl4 to PbCl4 as the metallic nature of the Group IV atom increases
    • When lead(IV) chloride is hydrolysed, a little decomposition of the lead(IV) chloride to lead(II) chloride also occurs
  • Group IV elements

    • C, Si and Ge have giant covalent structures; Sn and Pb are metals
    • Down Group IV, the elements show a general decrease in melting point and a general increase in metallic character and electrical conductivity
    • Group IV elements form covalently bonded tetrachlorides
  • The Group IV tetrachlorides are hydrolysed rapidly by water with the exception of carbon tetrachloride
  • Oxides, apart from CO and CO2

    • Solids with giant structures and high melting points
  • CO and CO2
    • Gases at room temperature, because they have a simple molecular structure with only weak forces between their molecules in the solid and liquid states
  • Carbon monoxide, CO
    Has a strong triple bond and does not decompose on heating
  • Germanium(II) oxide disproportionation
    2GeO(s)GeO2(s) + Ge(s)
  • Oxidation numbers of Germanium(II) oxide: +2, +4, 0
  • Tin(II) oxide, SnO, and lead(II) oxide, PbO

    • Do not decompose on heating in the absence of air, readily oxidised to higher oxides in the presence of oxygen
  • Carbon dioxide, CO2

    Has strong double bonds and does not decompose on heating
  • The oxides in the +4 oxidation state

    Tend to decrease in stability down the group, except lead(IV) oxide, PbO2, which undergoes significant thermal decomposition
  • Thermal decomposition of lead(IV) oxide
    PbO2(s) → PbO(s) + O(g)
  • Acid-base properties of oxides
    • CO - very weakly acidic
    • CO2 - acidic
    • SiO - very weakly acidic
    • SiO2 - amphoteric
    • GeO - amphoteric
    • GeO2 - amphoteric
    • SnO - amphoteric
    • SnO2 - amphoteric
    • PbO - amphoteric
    • PbO2 - amphoteric
  • The oxides in the +2 oxidation state

    Are less acidic (more basic) than the corresponding oxides in the +4 oxidation state
  • CO2 reaction with water

    CO2(g) + H2O →<— HCO3(aq) + H+(aq)
  • CO2 reaction with dilute alkalis
    CO2(g) + 2NaOH(aq) → Na2CO3(aq) + H2O
  • The oxides in both oxidation states

    Become more basic down the group as the metallic character of the Group IV atom increases
  • Reactions of carbon dioxide and silicon dioxide with alkalis

    • CO2 reacts with aqueous alkalis (hydroxide ions)
    • SiO2 only reacts with hot concentrated alkali
  • SiO2 reaction with hot concentrated alkali
    SiO2(s) + 2NaOH(aq)Na2SiO3(aq) + H2O
  • Amphoteric oxides of Group IV

    • GeO2, SnO and PbO are all amphoteric, but have increasingly basic character in the order GeO2 < SnO < PbO
    • They all react with acids to form a salt with oxidation state +2
    • They all react with alkalis to form ions with oxidation state +2
  • Amphoteric oxides of Group IV (oxidation state +2) reaction with acids
    SnO(s) + 2HCl(aq) → SnCl2(aq) + H2O
  • Amphoteric oxides of Group IV (oxidation state +2) reaction with alkalis
    1. GeO(s) + 2OH-(aq) → GeO2-(aq) + H2O
    2. SnO(s) + 2OH-(aq) → SnO2-(aq) + H2O
    3. PbO(s) + 2OH-(aq) → PbO2-(aq) + H2O
  • Amphoteric oxides of Group IV (oxidation state +4)

    • GeO2, SnO2 and PbO2 are all amphoteric
    • They all react with acids to form a salt with oxidation state +4
    • They all react with alkalis to form ions with oxidation state +4
  • Amphoteric oxides of Group IV (oxidation state +4) reaction with acids

    SnO2(s) + 4HCl(aq) → SnCl4(aq) + 2H2O
  • The relative stability of Group IV oxides in oxidation state +4
    Decreases down the group
  • The acidic character of the Group IV oxides in oxidation state +2 and +4

    Decreases down the group and the basic character increases
  • Group IV oxides in oxidation state +2 are more basic than the corresponding oxides in oxidation state +4
  • Carbon monoxide
    This gas is prepared in the laboratory by using warm concentrated sulphuric acid to dehydrate methanoic acid
  • Carbon monoxide
    • Burns with a pale blue flame
    • Forms carbon dioxide: 2CO(g) + O2(g) → 2CO2(g)
  • Carbon monoxide's most notorious characteristic
    Ability to bind tightly to haemoglobin in the blood, preventing haemoglobin from carrying oxygen around the body
  • Carbon monoxide gas forms as the result of incomplete combustion in petrol engines, and also in poorly ventilated gas fires, causing preventable deaths
  • Oxide character

    As a general rule, the metalloids are usually basic, although some can vary from non-metal to metal-like as the group is descended, becoming less acidic (i.e. more basic) as the atomic number increases
  • Carbon dioxide can dissolve in water to form a slightly acidic solution (pH=5)
  • Reaction of carbon dioxide in water
    1. CO2(g) + H2O → H2CO3(aq)
    2. H2CO3(aq) + H2O → HCO3-(aq) + H3O+