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1.
Oxide
There are two kinds of oxides of germanium, tin and lead.
MO is amphoteric and slightly alkaline, and MO 2 is amphoteric and acidic
.
SnO bluish-black · nH is SnO 2 O dehydration product temperature
.
SnO 2 is gray and is the product of the combustion of elemental Sn in the air
PbO is yellow, commonly known as Mi Tuo Seng or lead yellow.
It is the product of lead heating in the air, and it can also be obtained by thermal decomposition of PbCO 3 or Pb(NO 3 ) 2
.
PbO 2 is black and has strong oxidizing properties.
The strong oxidizing property of PbO 2 is related to the inert electron pair effect
.
Under alkaline conditions, NaCIO oxidizes Pb(II) salt to obtain PbO 2
.
Lead also has two important oxides, Pb 3 O 4 , and Pb 2 O 3
.
Pb 3 O 4 is red and is called red lead or plumbum.
Its composition is 2PbO·PbO 2 or written as Pb 2 [PbO 4 ]
Simple experiments can verify that both Pb 3 O 4 and Pb 2 O 3 oxides contain two valence states of lead
.
The oxide is dissolved in nitric acid , and the resulting black precipitate can oxidize Mn 2+ to MnO 4 - under acidic conditions , and Cl 2 is generated when reacting with HC1 , indicating that the precipitate is PbO 2
The black PbO 2 can be converted into red Pb 3 O 4 by heating to 374° C, and it can be converted into yellow PbO by heating to 605°C
.
2.
Hydroxide and oxyacid
Adding an appropriate amount of alkali dropwise to the solution of Sn 2+ and Pb 2+ can generate white precipitates Sn(OH) 2 and Pb(OH) 2
.
Sn(OH) 2 and Pb(OH) 2 are amphoteric and partial base, soluble in excess strong base
.
[Sn(OH) 4 ] 2- has strong reducibility and can reduce Bi 3+ to black elemental Bi powder
.
This reaction can be used to identify Bi3+
.
There are two configurations of stannate H 2 SnO 3 : aH 2 SnO 3 and β-H 2 SnO 3
.
aH 2 SnO 3 is chemically active, soluble in concentrated hydrochloric acid and alkali
β-H 2 SnO 3 is chemically inert, and it is neither soluble in concentrated acid nor soluble in concentrated alkali
.
The product of metal Sn dissolved in concentrated nitric acid is β-H 2 SnO 3
Related links: elemental germanium, tin, lead