204 GROUP IV
as copper(II) oxide) yield carbon dioxide, which gives a precipitate
of calcium carbonate when passed into aqueous calcium hydroxide.
Silicon
All silicon compounds on oxidation yield silica or silicates; these are
difficult to detect but silica (given by silicates after acid treatment) is
insoluble in all acids except hydrofluoric acid.
Tin
In presence of hydrochloric acid, tin(II) in aqueous solution (1) is
precipitated by hydrogen sulphide as brown SnS, and (2) will reduce
mercury(II) chloride first to rnercury(I) chloride (white precipitate)
and then to metallic mercury.
Tin(IV) in aqueous acid gives a yellow precipitate with hydrogen
sulphide, and no reaction with mercury(II) chloride.
Lead
Lead(II) in aqueous solution gives on addition of the appropriate
anion (1) a white precipitate of lead(II) chloride, (2) a yellow precipi-
tate of lead(II) chromate, and (3) a yellow precipitate of lead(II)
iodide which dissolves on heating and reappears on cooling in the
form of glistening 'spangles'.
QUESTIONS
- Compare and contrast the chemistry of silicon, germanium, tin
and lead by referring to the properties and bond types of their
oxides and chlorides.
Give brief experimental details to indicate how you could prepare
in the laboratory a sample of either tin(IV) chloride or tin(IV) iodide.
How far does the chemistry of the oxides and chlorides of carbon
support the statement that 'the head element of a group in the
Periodic Table is not typical of that group'? (JMB, A)
- What physical and chemical tests could you apply to the oxides
and chlorides of Group IV elements to show the changes in their
properties as the atomic number of the element increases? At the
