Peroxoacids. There are the following peroxoacids of sulfur: н2s2o8 is called peroxidisulfuric acid (supersulfuric acid), and н2so5 is peroxomonosulfuric acid (caro acid)

Uses

The production of ' superphosphate ' (calcium hydrogen phosphate + calcium sulfate) for fertilisers is the biggest use of sulfuric acid. Second to this is the manufacture of ammonium sulfate from ammonia (by the Haber process). This is also a fertiliser. Other uses are: conversion of viscose to cellulose in the manufacture of artificial silk, and so on; manufacture of explosives, pigments and dyestuffs, as well as many other chemicals, for example hydrochloric acid; refining of petroleum and sulfonation of oils to make detergents; and in accumulators.

Production. Н₂S₂O₈ is obtained electrolytically at the anode in 50% Н₂SO₄ aqueous solution:

2HSO₄^- = Н₂S₂O₈ + 2e

Н₂S₂O₈ can form peroxomonosulfuric acid (Caro acid) under the influence of concentrated Н₂O₂ (Heinrich Caro was a German organic chemist, who obtained this acid in 1898):

Н₂S₂O₈ + Н₂O₂ = 2Н₂SO₅

Structure. These acids are regarded as Н₂O₂ derivatives because groups —O—O— are present in their structure

Properties. Н₂S₂O₈ and Н₂SO₅ are crystalline substances. Their melting points make up 65^o and 47^o, respectively.

Н₂S₂O₈ is a strong dibasic acid. The O—H bond of the Caro acid dissociates strongly. At the same time, —O—O—H group (like hydrogen peroxide, K = 4∙10^-10) dissociates weakly. Therefore, it is a monobasic acid that is stable also in the free state. Salts exist only in solutions.

Peroxoacids and their salts are very strong oxidising agents due to the presence of —O—O— bonds:

2Mn⁺²SO₄ + 5K₂S₂O₈ + 8Н₂O = 2KMn⁺⁷O₄ + 4K₂SO₄ + 8Н₂SO₄

When heated with water Н₂S₂O₈ and Н₂SO₅ hydrolyse:

Н₂S₂O₈ + H₂O = Н₂SO₄ + H₂SO₅

H₂SO₅ + H₂O = Н₂SO₄ + H₂O₂ (industrial method of H₂O₂ production)

Дата добавления: 2014-01-11