Tin dioxide

Tin dioxide

Names
IUPAC name Tin (IV) Oxide
Other names Stannic oxide, Tin(IV) oxide, Flowers of tin,Cassiterite
Identifiers
CAS Number	18282-10-5 Y 13472-47-4 (hydrate) N
3D model (Jmol)	(O=Sn=O): Interactive image
ChemSpider	26988 N
ECHA InfoCard	100.038.311
EC Number	242-159-0
PubChem	29011
RTECS number	XQ4000000
InChI (O=Sn=O): InChI=1S/2O.Sn N Key: XOLBLPGZBRYERU-UHFFFAOYSA-N N
SMILES (O=Sn=O): O=[Sn]=O
Properties
Chemical formula	O2Sn
Molar mass	150.71 g·mol−1
Appearance	White or light grey powder
Odor	Odorless
Density	6.95 g/cm3 (20 °C) 6.85 g/cm3 (24 °C)
Melting point	1,630 °C (2,970 °F; 1,900 K)
Boiling point	1,800–1,900 °C (3,270–3,450 °F; 2,070–2,170 K) Sublimes
Solubility in water	Insoluble
Solubility	Soluble in hot concentrated alkalis, concentrated acids Insoluble in alcohol
Magnetic susceptibility (χ)	−4.1·10−5 cm3/mol
Refractive index (nD)	2.006
Structure
Crystal structure	Rutile tetragonal, tP6
Space group	P42/mnm, No. 136
Point group	4/m 2/m 2/m
Lattice constant	a = 4.737 Å, c = 3.185 Å α = 90°, β = 90°, γ = 90°
Coordination geometry	Octahedral (Sn4+) Trigonal planar (O2−)
Thermochemistry
Specific heat capacity (C)	52.6 J/mol·K
Std molar entropy (So298)	49.04 J/mol·K
Std enthalpy of formation (ΔfHo298)	−577.63 kJ/mol
Gibbs free energy (ΔfG˚)	−515.8 kJ/mol
Hazards
Safety data sheet	ICSC 0954
NFPA 704	0 1 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	> 20 g/kg (rats, oral)
US health exposure limits (NIOSH):
PEL (Permissible)	none
REL (Recommended)	TWA 2 mg/m3
IDLH (Immediate danger)	N.D.
Related compounds
Related tin oxides	Tin(II) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Tin dioxide (Tin (IV) oxide), also known as stannic oxide, is the inorganic compound with the formula SnO₂. The mineral form of SnO₂ is called cassiterite, and this is the main ore of tin. With many other names, this oxide of tin is the most important raw material in tin chemistry. It is a colourless, diamagnetic, amphoteric solid.

It crystallises with the rutile structure. As such the tin atoms are six coordinate and the oxygen atoms three coordinate. SnO₂ is usually regarded as an oxygen-deficient n-type semiconductor.

Hydrous forms of SnO₂ have been described as stannic acid. Such materials appear to be hydrated particles of SnO₂ where the composition reflects the particle size.

Tin(IV) oxide occurs naturally. Synthetic tin(IV) oxide is produced by burning tin metal in air. Annual production is in the range of 10 kilotons. SnO₂ is reduced industrially to the metal with carbon in a reverberatory furnace at 1200-1300 °C.

Although SnO₂ is insoluble in water, it is amphoteric, dissolving in base and acid. "Stannic acid" refers to hydrated tin (IV) oxide, SnO₂, which is also called "stannic hydroxide."

Tin oxides dissolve in acids. Halogen acids attack SnO₂ to give hexahalostannates, such as [SnI₆]²⁻. One report describes reacting a sample in refluxing HI for many hours.

Similarly, SnO₂ dissolves in sulfuric acid to give the sulfate:

SnO₂ dissolves in strong base to give "stannates," with the nominal formula Na₂SnO₃. Dissolving the solidified SnO₂/NaOH melt in water gives Na₂[Sn(OH)₆]₂, "preparing salt," which is used in the dye industry.

In conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides.