SULFUR DIOXIDE - (7446-09-5)

Introduction

Name: sulfur dioxide
* IUPAC
CAS Number: 7446-09-5
Chemical Formula: SO2
Molar Mass: 64.0638 g
Mass Percent: S 50.051 %; O 49.948 % 

Classification

• inorganic

Uses/Function

• "The most important use of sulfur dioxide is in the manufacture of sulfuric acid, but large quantities are used in bleaching organic coloring matters. Paper pulp, straw, silk, wool, and other materials which would be injured by chlorine can be decolorized by moist sulfur dioxide. The color of materials bleached by sulfur dioxide often returns on exposure to air, as in the case of straw. Bleaching by chlorine is permanent. Sulfur dioxide has been used extensively in refrigeration, but is being replaced by freons. Sulfur dioxide is used as a disinfectant. For this purpose, sulfur dioxide is burned, or liquid sulfur dioxide is allowed to escapein the space to be disinfected. In either case, the space should be tightly closed. Sulfur dioxide is also used to prevent the growth of mold. The minute quantity of sulfuric acid formed where sulfur dioxide is used with foodstuffs is immediately neutralized by alkalies present forming harmless salts." 1

• "...problems associated with the acid rain that SO2 produces..." 2

• "Gaseous sulfur dioxide is toxic to plants. At concentrations of 0.1 to 1 ppm, it inhibits growth and causes observable damage to leaves and flowers." 3

• "Today we realize that SO2 cannot be allowed to escape into the air. One way to remove it from the exhaust gases is to allow it to react with calcium carbonate...This method creates another problem, however - the disposal of solid calcium sulfite. Another way to dispose of the SO2 is to oxidize it to SO3. The SO3 can then be converted to sulfuric acid, which is then sold." 4

• "Sulfur dioxide, which is mostly made by burning sulfur and is usually marketed as the liquid (normal bp -10°C), has several uses:
(a) in extractive mineralogy, SO2 serves as a mild reductant, for example, in extracting iodine from Chilean sodium nitrate deposits and in processing uranium;
(b) in winemaking, sulfur dioxide is a widely used preservative, although it has the disadvantage that some people suffer severe allergic reactions to sulfur dioxide or sulfites (wines and dried fruits that contain sulfites must therefore be clearly labeled to that effect);
(c) SO2 is important in pulping and paper making; and
(d) in water treatment, SO2 can reduce, for example, excess chlorine used in water sterilization, or chromium(VI) in wastewater from electroplating plants and tanneries." 5

• "Dechlorination [in chemical water analysis]" 6

• "Sulfur dioxide from the burning of sulfur is also used in the bleaching of textile fibers and in the preparing of sulfite solutions for the production of paper pulp from wood." 7

Bonding

Double Bonds: 1
Triple Bonds: 0
Sigma Bonds: 2
Pi Bonds: 1
Total: 3
Carboxyl Groups: 0
Hydroxyl Groups: 0
Geometry: bent (V-shaped)
Hybridization: sp2
Bonding: polar covalent
Ionic Character: 26.06 %

Thermochemistry

ΔHf° (g): -70.944 kcal/mol 8 = -296.83 kJ/mol
S° (g): 59.30 cal/(mol•K) 9 = 248.11 J/(mol•K)
ΔGf° (g): -71.748 kcal/mol 10 = -300.19 kJ/mol

Reactions

As4S6 (s) + 9 O2 (g) → As4O6 (s) + 6 SO2 (g) 11
2 C2H5SH (ℓ) + 9 O2 (g) → 4 CO2 (g) + 6 H2O (g) + 2 SO2 (g) 12
CaCO3 (s) + 1 SO2 (g) → CaSO3 (s) + CO2 (g) 13
CaO (s) + 1 SO2 (g) → CaSO3 (s) 14
CS2 (ℓ) + 3 O2 (g) → CO2 (g) + 2 SO2 (g) 15
Cu (s) + 2 H2SO4 (ℓ) → CuSO4 (aq) + 2 H2O (ℓ) + 1 SO2 (g) 16
Cu2S (s alpha) + 1 O2 (g) → 2 Cu (s) + SO2 (g) 17
2 CuFeS3 (s) + 7 O2 (g) → 6 Cu (s) + 2 FeO (s) + 6 SO2 (g) 18
2 CuS + 1 O2 → Cu2S + SO2  19
2 H2S (g) + 3 O2 (g) → 2 H2O (ℓ) + 2 SO2 (g) 20
2 H2S (g) + 3 O2 (g) → 2 H2O (g) + 2 SO2 (g) 21
16 H2S (g) + 8 SO2 (g) → 16 H2O (g) + 3 S8 (s) 22
H2SO3 (aq) → SO2 (g) + H2O (ℓ) 
2 HCl (aq) + 1 Na2SO3 (s) → 2 NaCl (aq) + H2O (ℓ) + 1 SO2 (g) 
2 MoS2 (s) + 7 O2 (g) → 2 MoO3 (s) + 4 SO2 (g) 23
Na2SO3 (aq) + 2 HCl (aq) → 2 NaCl (aq) + H2O (ℓ) + 1 SO2 (g) 24
P4S3 (s) + 8 O2 (g) → P4O10 (s) + 3 SO2 (g) 25
PbS + 1 O2 → Pb + SO2  26
2 PbS (s) + 3 O2 (g) → 2 SO2 (g) + 2 PbO (s red) 27
S8 (s) + 8 O2 (g) → 8 SO2 (g) 28
SF4 (g) + 2 H2O (ℓ) → SO2 (g) + 4 HF (ℓ) 29
2 SO2 (g) + 1 O2 (g) → 2 SO3 (g) 30
2 SO2 (g) + 2 CaCO3 (s) + 1 O2 (g) → 2 CaSO4 (s) + 2 CO2 (g) 31
2 ZnS (s sphalerite) + 3 O2 (g) → 2 ZnO (s) + 2 SO2 (g) 32
2 H2S (g) + 1 SO2 (g) → 3 S (s rhombic) + 2 H2O (ℓ) 33
2 H3PO4 (aq) + 3 Na2SO3 (s) → 2 Na3PO4 (aq) + 3 H2O (ℓ) + 3 SO2 (g) 
2 HBr (aq) + 1 Ag2SO3 (s) → 2 AgBr (s) + H2O (ℓ) + 1 SO2 (g) 
2 HI (aq) + 1 Ag2SO3 (s) → 2 AgI (s) + H2O (ℓ) + 1 SO2 (g) 
2 HI (aq) + 1 Na2SO3 (s) → 2 NaI (aq) + H2O (ℓ) + 1 SO2 (g) 
Na2SO3 (aq) + 2 HCN (ℓ) → 2 NaCN (aq) + H2O (ℓ) + 1 SO2 (g) 

For More Information

Sources

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