Is sulfurous acid a strong acid or a weak acid?

Sulfurous acid is a very transparent liquid with the smell of sulfur dioxide. It is very easy to decompose and dissolve in water. Sulfurous acid is also widely used. For example, it can be used as an analytical reagent, a reducing agent or a preservative. However, it is harmful to the eyes, skin, mucous membranes and many other parts of the human body. So is sulfurous acid a strong acid or a weak acid?

First, is sulfurous acid a strong acid or a weak acid? Common weak acids: H2SiO3 (metasilicic acid), HCN (hydrocyanic acid), H2CO3 (carbonic acid), HF (hydrofluoric acid, less common), CH3COOH (also known as C2H4O2 acetic acid, also called acetic acid), H2S (hydrogensulfuric acid), HClO (hypochlorous acid), HNO2 (nitrous acid, less common), all organic acids within the scope of middle school (strong organic acids are not studied in middle school), and H2SO3 (sulfurous acid) are also weak acids. Medium strong acids: H2SO3, H3PO4, HF, H2C2O4 (oxalic acid/oxalic acid). Strong acids: permanganate, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid (HClO4), selenic acid, hydrobromic acid, hydroiodic acid, and chloric acid (HClO3). Among them, perchloric acid, hydroiodic acid, hydrobromic acid, hydrochloric acid (hydrochloric acid), sulfuric acid, and nitric acid are collectively known as the six major inorganic strong acids.

Second, the aqueous solution of sulfur dioxide is called sulfurous acid, which is actually a hydrate, SO2·xH2O. Free sulfurous acid has not yet been produced; it only exists in aqueous solution. The following equilibrium exists in an aqueous solution of sulfurous acid: SO2+xH2O = SO2·xH2O = H++HSO3- +(x-1)H2O, K1=1.54×10-2(291K); HSO3-= H++SO32-, K2=1.02×10-7(291K). When acid is added and heated, the equilibrium shifts to the left and SO2 gas escapes. When alkali is added, the equilibrium shifts to the right, forming an acid salt or a normal salt.

NaOH+SO2=NaHSO3; 2NaOH+SO2=Na2SO3+H2O In sulfurous acid and sulfites, the oxidation number of sulfur is +4. So sulfurous acid and sulfites have both oxidizing and reducing properties, but their reducing property is dominant. Sulfites are more reducing than sulfurous acid. Alkali metal sulfites are easily soluble in water, and due to hydrolysis, the solution becomes alkaline. The normal salts of other metals are slightly soluble in water. All acid sulfites are readily soluble in water. Sulfites are easily decomposed by heat.

Is sulfurous acid a strong acid or a weak acid? Sulfous acid H2SO3 can be rewritten as: (HO)2SO1 n=1, so it is a weak acid. Principle: (HO)mROn n=3 is the strongest acid, n=2 is a strong acid, n=1 is a weak acid, n=0 is an extremely weak acid

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