Chemical reactions

Reaction of tin with air

Under normal conditions tin does not react with air. When heated, tin reacts with oxygen, O2, forming tin dioxide, SnO2.

Sn(s) + O2(g) SnO2(s)

Reaction of tin with halogens

Tin reacts with Cl2 forming tin(IV)chloride [6].

Sn(s) + 2 Cl2(g) SnCl4(s)

Reaction of tin with hydroxide ions

Sn(II) is precipitated by hydroxide ions as a white gelatinous precipitate [6]:

Sn2+(aq) + 2 OH(aq) Sn(OH)2(s) [white]

The precipitate is dissolved in excess alkali [6]:

Sn(OH)2(s) + 2 OH(aq) [Sn(OH)4]2−(aq)

Reaction of tin with metals/metal ions

Sn(II) is oxidized by Hg22+. This reaction is used for qualitative analysis for Sn(II):

Hg22+(aq) + Sn2+(aq) 2 Hg(l) + Sn4+(aq)

Under acidic conditions and in the presence of chloride ions, Hg(II) is reduced to Hg(I) by Sn(II), forming Hg2Cl2:

Hg2+(aq) + Sn2+(aq) + 2 Cl(aq) Hg2Cl2(s) + Sn4+(aq)

In excess Sn(IV), Hg(I) is reduced to Hg:

Hg2Cl2(s) + Sn2+(aq) 2 Hg(l) + Sn4+(aq) + 2 Cl(aq)

Sn(IV) is reduced by Fe to Sn(II) in HCl(aq)

[SnCl6]2−(aq) + Fe(s) [SnCl3](aq) + Fe2+(aq) + 3 Cl(aq)

Manganese with oxidation steps >2 will be reduced to Mn(II) by Sn(II) under acidic conditions under the formation of Sn(IV), e.g.

MnO2(s) + Sn2+(aq) + 4 H+(aq) Mn2+(aq) + Sn4+(aq) + 2 H2O(l)

Reaction of tin with peroxide

Sn(II) is easily oxidized to Sn(IV) by hydrogen peroxide under acidic conditions

[SnCl3](aq) + H2O2(aq) + 2 H+(aq) [SnCl6]2−(aq) + 2 H2O(l)

Reaction of tin with sulfide

Sn(II) is precipitated by hydrogensulfide in 0.4M HCl(aq):

Sn2+(aq) + H2S(aq) SnS(s) [brown/black] + 2 H+(aq)

In strong acid, the precipitate is dissolved:

SnS(s) + 2 H+(aq) + 3 Cl(aq) [SnCl3](aq) + H2S(g)

The precipitate is also dissolved in Na2S2 but not in Na2S:

SnS(s) + S22−(aq) [SnS3]2−(aq)

Sn(IV) is precipitated by hydrogensulfide in moderately acidic solutions [6]:

[SnCl6]2−(aq) + H2S(aq) SnS2(s) [yellow] + 4 H+(aq) + 6 Cl(aq)

The precipitate is dissolved in alkali metal sulfides, forming thiostannate ions, and concentrated hydrochloric acid [6]:

SnS2(s) + S2−(aq) [SnS3]2−(aq)
SnS2(s) + 4 H+(aq) + 6 Cl(aq) [SnCl6]2−(aq) + H2S(aq)

When an alkali metal hydroxide is added, a white precipitate is formed. The precipitate is not Sn(OH)4, as could be expected. It may be orthostannic acid H2[Sn(OH)6] [6]

Reaction of tin with water

Tin does not react with water under normal conditions. When exposed to steam, tin dioxide, SnO2 and hydrogen are formed.

Sn(s) + 2 H2O(g) SnO2(s) + 2 H2(g)

Sn(IV) is precipitated as α-tin acid upon hydrolysis of Sn(IV) solutions:

[SnCl6]2−(aq) + 6 H2O(l) H2[Sn(OH)6](s) + 4 H+(aq) + 6 Cl(aq)

The precipitate is amphoteric and is dissolved in acids and strong alkali:

H2[Sn(OH)6](s) + 2 OH(aq) [Sn(OH)6]2−(aq) + 2 H2O(l)
H2[Sn(OH)6](s) + 4 H+(aq) + 6 Cl(aq) [SnCl6]2−(aq) + 6 H2O(l)

Quantitative analysis

Method 3500-Sn B Atomic Absorption Spectrometric Method [2]. A portion of the sample is digested in a combination of acids. The digest is atomized in a graphite tube and resulting absorption of light is measured at 235.5 nm.

Method limit of detection in water = 0.002 mg/L
Method limit of detection in soil = 0.50 mg/kg