Nitrogen, standard reduction potentials

Table 11.4 Standard reduction potentials for nitrogen species in acidic aqueous solution (pH 0, 25°C)...

Tlic power of these various concepts in codifying and rationalizing the redox chemistry of the clcineiUs is ilhislraled for Ihe case of nitrogen in tbe present section Standard reduction potentials and plots of volt equivalents against oxidation state fur odicr elements are presented in later chapters... 

Figure 11.8 Oxidation states of nitrogen showing standard reduction potentials in volts (a) in acid solution at pH 0, and (b) in basic solution at pH 14.

See also The Nitrogen Cycle, Nitrate Utilization, Standard Reduction Potential (from Chapter 15), Ferredoxin... 

The stepwise reduction of NO2 to NO occurs at standard reduction potentials very close to the standard potential for the reduction of O2 to H2O (Table 15.1, Eqs. (15.1-15.3)). This relationship implies that NO cocatalysts are able to capture nearly the full thermodynamic driving force of O2 as a terminal oxidant [4]. This favorable feature, together with the kinetically facUe oxidation of NO to NO2 (Table 15.1, Eq. (15.4)), contributes to the effectiveness of NO -based cocatalysts in aerobic oxidation reactions. Depending on the reaction conditions, NO2 can equilibrate with other nitrogen oxide species, such as N2O4, and NO, which could also serve as catalytically relevant oxidants in NO -catalyzed aerobic alcohol oxidation reactions (Eq. (15.5)) [5]. 

The two common oxyacids of nitrogen are nitric acid (HNO3) and nitrous acid (HNO2) ( FIGURE 22.26). Nitric acid is a strong acid. It is also a powerful oxidizing agent, as indicated by the standard reduction potential in the reaction... 

M Figure 22.30 Standard reduction potentials in acid solution for some common nitrogen-containing compounds. Reduction of NO3 to NO2 in acid solution, for example, has a standard electrode potential of 0.79 V (leftmost entry). You should be able to balance this half-reaction using the techniques discussed in Section 20.2. 

Chloramine, like chlorine, is an oxidizing biocide used for disinfection. Three species collectively make up chloramines, also known as combined chlorine monochloramine, NH Cl dichloramine, NHCl and nitrogen trichloride (trichloramine), NCI3. Of these, monochloramine has the highest standard reduction potential furthermore, it is less prone to impart chlorinous taste and odor to water like other forms of chloramine. As a result, monochloramine is preferred for disinfection applications. 

Balance the reaction shown below in which nitrogen dioxide disproportionates to nitrous add and nitrate ions in add solution. Use the standard reduction potentials given to determine if this disproportionation reaction would actually occur under standard-state conditions. 

Reductions. Hydrazine is a very strong reducing agent. In the presence of oxygen and peroxides, it yields primarily nitrogen and water with more or less ammonia and hydrazoic acid [7782-79-8]. Based on standard electrode potentials, hydrazine in alkaline solution is a stronger reductant than sulfite but weaker than hypophosphite in acid solution, it falls between and Ti ( 7). 

The reduction potential of compounds containing N-F bonds is strongly affected by the substituents on the nitrogen. In the series studied, a shift of the measured reduction potential of the N-F bond of about 2 V was observed, which represents a difference of the standard free energy charge associated with the electron transfer of more than 45 kcal mol - . 

In a fuel cell, hydrazine, N2H4, is oxidised to nitrogen, and oxygen is reduced to water. The standard electrode potentials for the reduction of N2 to N2H4 and of O2 to H2O at 298 K are —1.155 V and +0.401 V, respectively, both under alkaline conditions. 

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