Question

Sulphur dioxide to sulphurous acid using neutral liquid

Answer 1

Explanation:

Sulfurous Acid

Sulfurous acid has the formula H2SO3 and the molecular weight of 82.075 g/mol. Its CAS number is 7782-99-2. There is no clear evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase. The conjugate bases of this elusive acid are, however, common anions: bisulfite (or hydrogensulfite) = HSO3− and sulfite, SO3=. Bisulfite salts are typically prepared by treatment of alkaline solutions with excess sulfur dioxide:

SO2 + NaOH ⇒ NaHSO3

HSO

−

3

is the conjugate base of sulfurous acid, H2SO3 and its appearance is a function of solution pH:

H2SO3 ⇔ HSO3− + H+

Sulfurous acid has not been isolated as a separate compound and does not appear to exist in solution either. An equilibrium that is much more consistent with spectroscopic evidence is given as:

SO2 + H2O ⇔ HSO3− + H+

HSO

−

3

is a weak acidic species with a pKa of 6.97. Its conjugate base is the sulfite anion, SO

2−

3

:

HSO

−

3

⇔ SO

2−

3

+ H+

Bisulfites are reducing agents, as are all sulfites and sulfur dioxide, which contains sulfur in the same oxidation state of +5. Raman spectra of solutions of sulfur dioxide in water show only signals due to the SO2 molecule and the bisulfite ion, HSO3−. The intensities of the signals are consistent with the following equilibrium:

SO2 + H2O ⇔ HSO

−

3

+ H+

Ka = 1.54 × 10−2; pKa = 1.81.

Aqueous solutions of sulfur dioxide, which sometimes are referred to as “sulfurous acid” are used as reducing agents and as disinfectants, as are solutions of bisulfite and sulfite salts. They are also mild bleaches, and are used for materials that may be damaged by chlorine-containing bleaches.

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Answer 2

Answer:

Sulphur dioxide to sulphurous acid using a neutral liquid