Homogeneous catalysis hydrogen peroxide decomposition

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

An example of a reaction that is subject to homogeneous catalysis is the decomposition of hydrogen peroxide in aqueous solution ... 

The most numerous cases of homogeneous catalysis are by certain ions or metal coordination compounds in aqueous solution and in biochemistry, where enzymes function catalytically. Many ionic effects are known. The hydronium ion H3O and the hydroxyl ion OH catalyze hydrolyses such as those of esters ferrous ion catalyzes the decomposition of hydrogen peroxide decomposition of nitramide is catalyzed by acetate ion. Other instances are inversion of sucrose by HCl, halogenation of acetone by H and OH , hydration of isobutene by acids, hydrolysis of esters by acids, and others. 

In the section 2.3. we presented catalysis by complexes of transition metals and argued that this type of homogeneous catalysis is gaining importance in industrial processes. Kinetic models of several reactions will be considered in the next paragraph. Here we would like to address reactions where the metal ions act as catalysts. As an example of such a process, hydrogen peroxide decomposition will be considered. Transition metals, mainly manganese, iron and copper, are effcient catalysts for this reaction. 

A FIGURE 14.22 Homogeneous catalysis. Effect of catalyst on the speed of hydrogen peroxide decomposition to water and oxygen gas. 

We have just described the homogeneous catalysis of the decomposition of hydrogen peroxide. The decomposition can also be catalyzed by heterogeneous catalysis, as seen at the bottom of page 961. 

Many investigations of the decomposition of hydrogen peroxide involving base catalysis have been made these have been reviewed . The extent to which the surface of glass vessels can control such rates has been emphasised . The rates of the homogeneous reaction have been measured , after scrupulous attention to purification. Then the rate equation is... 

Another example of homogeneous catalysis is that of the decomposition of hydrogen peroxide by bromide ion. Here hydrogen peroxide acts as both an oxidant and a reductant, with two different reactions proceeding at characteristic rates under a given set of conditions ... 

Many examples of what is now called catalysis, both homogeneous and heterogeneous, were known early in the nineteenth century. The Dutch chemists (see Vol. Ill, p. 584) had observed the contact action of metals and oxides Davy (see p. 69), Thenard (see p. 92), Dobereiner (see p. 179), and Faraday (see p. 109) that of platinum and other metals in decomposition and combustion reactions of gases, and Thenard (see p. 93) the action of metals in the decomposition of hydrogen peroxide. These are examples of heterogeneous catalysis. Less well known were examples of homogeneous catalysis, particularly in the conversion of starch into sugar. 

Homogeneous catalysis often involves changes in oxidation number of the ions involved in catalysis. For example, small amounts of iodide ions catalyse the decomposition of hydrogen peroxide. In the catalysed reaction, iodide ions, H, are first oxidised to iodate(I) ions, 10. The IQ- ions then react with further molecules of hydrogen peroxide and are reduced back to iodide ions. 

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