Tin

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Tin
Chemical formula Sn
Atomic Number 50 
OTP appearance grey solid 
Molar Mass(g/mol) 118.7 
Melting Point(°C) 231.93 
Boiling Point(°C) 2602 
Density(g/cc) 7.365 
Coefficient of Thermal Expansion(×10-6 °C-1) 23.8
NFPA 704
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Uses

Primary

  • as a component of bronze, brass and pewter.
  • as a component of solder

Secondary

  • tin is a useful structural material where its malleable nature is used, such as hinges or crimpable fasteners

Natural Sources

  • Elemental tin does not occur naturally
  • -oxide occurrs naturally as cassiterite

Hazards

  • Virtually all organotin compounds are highly toxic
  • At temperatures below 14°C, tin undergoes an allotropic change which changes the tin from a metallic form to a nonmetallic form. This is called "tin blight" or "tin pest". This process slowly reverses above 14°C and is rapidly reversed above 100°C.

Character

  • Tin has two important allotropes:
    • α- or "grey" tin which is grey, brittle, and nonmetallic.
    • β- or "white" tin which is silvery, ductile and metallic.
  • At 13.2 °C and below, pure Β tin transforms to α-tin
  • At 100°C and above α-tin reverts to Β-tin.

Production

Extraction

Reduction of tin with carbon is not an easy process since the free energies of reduction are unfavorable.

SnO2 + C Sn + CO2ΔH=+125.2 kJ

However, reduction with carbon monoxide is considerably less unfavorable. For the reaction

SnO2 + CO SnO + CO2ΔH=+5.5 kJ // First oxygen
SnO + CO Sn + CO2ΔH=-0.3 kJ // Second oxygen
SnO2 + 2 CO 2 CO2 + SnΔH=+5.2kJ // Net

Testing

Storage

  • stacked as ingots, keeping the temperature above 14°C

Disposal

See Also

References