Physical properties of sulfur dioxide

Update:14-12-2019
Summary:

  Sulfur dioxide is a colorless transparent gas. T […]

 

Sulfur dioxide is a colorless transparent gas.

Three resonance structures of sulfur dioxide

Has an irritating odor. Soluble in water, ethanol and ether.

Liquid sulfur dioxide is relatively stable and inactive. Gaseous sulfur dioxide does not decompose when heated to 2000 ° C. Does not burn or form explosive mixtures with air.

Inorganic compounds such as bromine, boron trichloride, carbon disulfide, phosphorus trichloride, phosphoryl chloride, iodine chloride, and various thionyl chlorides can be mixed with liquid sulfur dioxide in any proportion. The solubility of alkali metal halides in liquid sulfur dioxide decreases in the order of I-> Br-> Cl-. Most metal oxides, sulfides, sulfates, etc. are insoluble in liquid sulfur dioxide.

Sulfur dioxide is a curved molecule whose symmetry point group is C2v. The sulfur atom has an oxidation state of +4, a formal charge of 0, and is surrounded by 5 electron pairs, so it can be described as a supervalent molecule. From the viewpoint of molecular orbital theory, it can be considered that most of these valence electrons participate in the formation of S-O bonds. The S-O bond length (143.1 pm) in sulfur dioxide is shorter than the S-O bond length (148.1 pm) in sulfur monoxide, and the O-O bond length (127.8 pm) in middle is longer than the O-O bond length (120.7 pm) in oxygen. The average bond energy of sulfur dioxide (548 kJ · mol-1) is larger than the average bond energy of SO (524 kJ · mol-1), and the average bond energy (297 kJ · mol-1) is smaller than the average bond energy of O2 ( 490 kJ · mol-1). These evidences led chemists to conclude that the S-O bond in sulfur dioxide has a bond level of at least two, and unlike the O-O bond in ozone, the O-O bond in ozone has a bond level of 1.5.

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