Does water react with the sulfuric acid

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Sulfuric acid reactivity


In aqueous solution, sulfuric acid splits off protons in two stages (and).

H2SO4 is a very strong acid (= -3), HSO4- is a strong acid (= 1.9). Sulfuric acid is a dibasic acid. Their salts are called hydrogen sulfates (primary sulfates, acid sulfates, bisulfates) or sulfates (secondary sulfates, neutral sulfates).

Reaction with water

Concentrated sulfuric acid has a great affinity for water. The dehydrating effect of concentrated sulfuric acid is used to dry chemical substances and to remove water from chemical equilibria.

Sulfuric acid forms an azeotrope with water, which consists of 98% sulfuric acid and 2% water and boils at 338.


At temperatures above 300, sulfuric acid breaks down into anhydride and water.

If sulfuric acid is evaporated in this way, one speaks of "fuming off" the acid.

Oxidizing effect

Dilute sulfuric acid reacts with base metals to produce hydrogen. This is an important method for producing hydrogen in the laboratory.

Concentrated sulfuric acid reacts with more noble metals (copper, mercury or silver) with reduction to sulfur dioxide.

Detection reaction

Sulfuric acid and sulfates are detected as poorly soluble, finely crystalline barium sulfate by precipitation with barium chloride.