Oxidizing strength

A summary of oxidation-reduction half-reactions arranged in order of decreasing oxidation strength and useful for selecting reagent systems. 

Rubber-lined steel For dilute not concentrated (oxidizing) strengths temperature limited according to rubber hardness and acid concentration steel fabrication must be properly done... 

Halogen Melting point (°C) Boiling point (°C) Vapour density (air = 1.0) Threshold limit value (ppm) Reactivity and oxidizing strength Appearance and state at 21 " C Colour of gas/vapour... 

Suong oxidizers have more potential incompatibilities than perhaps any other chemical group (with the exception of water reactive substances). It is safe to assume that they should not be stored or mixed with any other material except under carefully controlled conditions. Common oxidizing agents listed in decreasing order of oxidizing strength include ... 

Section 1.9 showed that as long as an oxide layer remains adherent and continuous it can be expected to increase in thickness in conformity with one of a number of possible rate laws. This qualification of continuity is most important the direct access of oxidant to the metal by way of pores and cracks inevitably means an increase in oxidation rate, and often in a manner in which the lower rate is not regained. In common with other phase change reactions the volume of the solid phase alters during the course of oxidation it is the manner in which this change is accommodated which frequently determines whether the oxide will develop discontinuities. It is found, for example, that oxidation behaviour depends not only on time and temperature but also on specimen geometry, oxide strength and plasticity or even on specific environmental interactions such as volatilisation or dissolution. 

Based on the relative oxidizing strengths of the cations obtained in Question 88, which of the following reactions would you expect to occur ... 

As you might expect from the half-equation for its reduction, the oxidizing strength of the dichromate ion decreases as the concentration of H+ decreases (increasing pH). 

Oxoacid (continued) acid strength of, 567-568 oxidizing strength, 568-570 reducing strength of, 568-570 Oxoacids, 42... 

Self-Test 15.5A Predict the trend in oxidizing strength of the halogens in aqueous solution. 

The interhalogens have properties intermediate between those of the constituent halogens. Nonmetals form covalent halides metals tend to form ionic halides. The oxoacids of chlorine are all oxidizing agents both acidity and oxidizing strength of oxoacids increase as the oxidation number of the halogen increases. 

Predict the relative oxidizing strengths of H2Xe04 and H4Xe06. Explain your conclusions. 

Refer to Appendix 2B and arrange the halogens in order of increasing oxidizing strength in water. 

Fig. 1.14. A scheme of the effect of the rise in atmospheric oxygen on the balance of oxidation states of several elements in the environment. The lines are drawn as oxidation strengths of elements at pH 7.0 against an H+/H2 oxidising power of —0.42 V at this pH. The initial balance of each element some 4 x 109 years ago is close to the H+/H2 line, hence many are reduced, while the state today is close to the 02/H20 line, whence many are oxidised. Thus in time, elements have moved from reduced states to oxidised states seen in their balances, which can be calculated, see Table 6.1. We are only concerned here with inorganic and not with bio-organic chemistry.

Recently, Muha (83) has found that the concentration of cation radicals is a rather complex function of the half-wave potential the concentration goes through a maximum at a half-wave potential of about 0.7 V. The results were obtained for an amorphous silica-alumina catalyst where the steric problem would not be significant. To explain the observed dependence, the presence of dipositive ions and carbonium ions along with a distribution in the oxidizing strengths of the surface electrophilic sites must be taken into account. The interaction between the different species present is explained by assuming that a chemical equilibrium exists on the surface. 

The halic acids may not be industrially important, but their salts certainly are. Sodium chlorate is produced in enormous quantities and used in processes in which its oxidizing strength makes it a versatile bleach. One such use is in making paper, and potassium chlorate is used as the oxidizing agent in matches. The decomposition of potassium chlorate was discussed in Chapter 13 in connection with the laboratory preparation of oxygen. 

F2 has the most positive standard reduction potential and therefore is the strongest of all common oxidizing agents. Oxidizing strengths of the diatomic halogen molecules decrease down Group 7A. 

Based upon thermodynamic data given in Table I, oxidant strength decreases in the order NijO > Mn02 > MnOOH > CoOOH > FeOOH. Rates of reductive dissolution in natural waters and sediments appear to follow a similar trend. When the reductant flux is increased and conditions turn anoxic, manganese oxides are reduced and dissolved earlier and more quickly than iron oxides (12, 13). No comparable information is available on release of dissolved cobalt and nickel. 

The redox potential of the acceptor excited state, Ejed (Eq. 12), defines its oxidative strength PET is limited to substrates with oxidation potentials below... 

If the following reactions are spontaneous, arrange the elements Fe, Ni, Cu, Ca, and Zn in order of increasing tendency to give electrons (oxidation strength). 

Solid sodium bismuthate (NaBi03) has an oxidizing strength similar to that of Ag2+ and S201. Excess solid oxidant is removed by filtration. 

H.9 The powerful oxidizing strength of iFeO j2- is shown by its ability to liberate oxygen from water and to produce dmitrogen from ammonia Write balanced equations for these two reactions. 

We live under a blanket of the powerful oxidant 02. By cell respiration oxygen is reduced to H20, which is a very poor reductant. Toward the other end of the scale of oxidizing strength lies the very weak oxidant H+, which some bacteria are able to convert to the strong reductant H2. The 02 -H20 and H+ - H2 couples define two biologically important oxidation-reduction (redox) systems. Lying between these two systems are a host of other pairs of metabolically important substances engaged in oxidation-reduction reactions within cells. 

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