Of nitrate ion

The effect of potassium nitrate on the rate arises in a similar way. The concentration of nitrate ions in concentrated nitric acid is appreciable, and addition of small quantities of nitrate will have relatively little effect. Only when the concentration of added nitrate exceeds that of the nitrate present in pure nitric acid will the anticatalysis become proportional to the concentration of added salt. 

The addition of water depresses zeroth-order rates of nitration, although the effect is very weak compared with that of nitrate ions concentrations of 6x io mol 1 of water, and 4X io mol 1 of potassium nitrate halve the rates of reaction under similar conditions. In moderate concentrations water anticatalyses nitration under zeroth-order conditions without changing the kinetic form. This effect is shown below (table 3.5) for the nitration of toluene in nitromethane. More strikingly, the addition of larger proportions of water modifies the kinetic... 

If we consider the effect of nitrous acid upon zeroth-order nitration in organic solvents we must bear in mind that in these circumstances dinitrogen tetroxide is not much ionised, so the measured concentration of nitrous acid gives to a close approximation the concentration of dinitrogen tetroxide. Further, the negligible self-ionisation of nitric acid ensures that the total concentration of nitrate ions is effectively that formed from dinitrogen tetroxide. Consequently as we can see from the equation for the ionisation of dinitrogen tetroxide ( 4.3.1),... 

The weak effect of nitrous acid upon nitration in nitric acid is a consequence of the already considerable concentration of nitrate ions supplied in this case by the medium. 

The effect of acetate ions cannot be distinguished from that of nitrate ions, which... 

Considering first pure nitric acid as the solvent, if the concentrations of nitronium ion in the absence and presence of a stoichiometric concentration x of dinitrogen tetroxide are yo and y respectively, these will also represent the concentrations of water in the two solutions, and the concentrations of nitrate ion will be y and x- y respectively. The equilibrium law, assuming that the variation of activity coefficients is negligible, then requires that ... 

The negative charge is shared equally by all three oxygens Stabilization of nitrate ion by electron delocalization increases the equilibrium constant for its formation... 

A slight but systematic decrease in the wave number of the complexes bond vibrations, observed when moving from sodium to cesium, corresponds to the increase in the covalency of the inner-sphere bonds. Taking into account that the ionic radii of rubidium and cesium are greater than that of fluorine, it can be assumed that the covalent bond share results not only from the polarization of the complex ion but from that of the outer-sphere cation as well. This mechanism could explain the main differences between fluoride ions and oxides. For instance, melts of alkali metal nitrates display a similar influence of the alkali metal on the vibration frequency, but covalent interactions are affected mostly by the polarization of nitrate ions in the field of the outer-sphere alkali metal cations [359]. 

Solutions of cerium(IV) sulphate may be prepared by dissolving cerium(IV) sulphate or the more soluble ammonium cerium(IV) sulphate in dilute (0.5-1.0M) sulphuric add. Ammonium cerium(IV) nitrate may be purchased of analytical grade, and a solution of this in 1M sulphuric add may be used for many of the purposes for which cerium(IV) solutions are employed, but in some cases the presence of nitrate ion is undesirable. The nitrate ion may be removed by evaporating the solid reagent which concentrated sulphuric add, or alternatively a solution of the nitrate may be predpitated with aqueous ammonia and the resulting cerium(IV) hydroxide filtered off and dissolved in sulphuric acid. 

The acid concentration of the solution must not be too great, otherwise the deposition of the copper may be incomplete or the deposit will not adhere satisfactorily to the cathode. The beneficial effect of nitrate ion is due to its depolarising action at the cathode ... 

The electrolytic deposit should be salmon-pink in colour, silky in texture, and adherent. If it is dark, the presence of foreign elements and/or oxidation is indicated. Spongy or coarsely crystalline deposits are likely to yield high results they arise from the use of too high current densities or improper acidity and absence of nitrate ion. 

Discussion. Dead-stop end point titrimetry may be applied to the determination of nitrate ion by titration with ammonium iron( II) sulphate solution in a strong sulphuric acid medium ... 

Determine the end point from the plot of current against volume of iron reagent. Calculate the weight of nitrate ion equivalent to 1.0 mL of the 0.4 M iron solution. 

When dealing with small amounts of nitrate ion it is advisable to pass a current of pure nitrogen through the solution before commencing the titration, and to maintain an atmosphere of nitrogen in the flask throughout the titration. 

The effect of nitrous acid on nitration in nitromethane and acetic acid is also attributed to the effect of nitrate ions even though the ionisation of the dinitrogen tetroxide is much less in these solvents. As noted above (p. 31), the anticatalytic effect of nitrous acid is not governed by k x = a+6[HN03] at nitrous acid concentrations above 0.1 M. 

Growing plants require a variety of chemical elements. Nitrogen, phosphorus, and potassium are required in the greatest amounts, but plants also need trace amounts of calcium, copper, iron, zinc, and other elements. By far the most substantial need is for nitrogen. The Earth s atmosphere is 80% molecular nitrogen, but plants cannot use N2. Instead, most plants absorb nitrogen from the soil in the form of nitrate ions. 

The accelerating effect of nitrate ions (over the range 10 to 1.0 M, at /i = 3.68 A/) has also been studied . An additional pathway involving the species TlNOj ", ... 

Nitration can be catalyzed by lanthanide salts. For example, the nitration of benzene, toluene, and naphthalene by aqueous nitric acid proceeds in good yield in the presence of Yb(03SCF3)3.5 The catalysis presumably results from an oxyphilic interaction of nitrate ion with the cation, which generates or transfers the N02+ ion.6 This catalytic procedure uses a stoichiometric amount of nitric acid and avoids the excess strong acidity associated with conventional nitration conditions. 

It will be instructive to explain the matter stated above by an example. The conductance of silver in solution at 18 °C is given as 55.7 and of nitrate ion as 60.8. The specific conductivity (K) of AgN03 in N/10 solution at 18 °C is 0.00947 mhos. From all these given data it is the aim of the present example to calculate the percentage of dissociation of the salt at its given concentration. It may be noted that in this illustration the specific conductivity (K) in N/10 solution is 0.00947 mhos. The volume containing 1 g-equiv. is 10,000 ml. Therefore,... 

A violent explosion ocurred during prolonged azeotropic drying at 105-110°C of a 75 wt% benzene solution of the salt. Traces of a nitrate ester may have been formed from a slight excess of nitrate ion. 

We separate the given equation into its two half-equations. One of them is the reduction of nitrate ion in acidic solution, whose standard half-cell potential we retrieve from Table 21-1 and use to solve the problem. 

In 1945, H. H. Comly first estimated the correlation between nitrates in drinking water and the incidence of methemoglobinemia. Research shortly afterwards showed that no cases of methemoglobinemia had been reported in any area of the United States where the water supply contained less than 45 ppm of nitrate ion. This value has become accepted in USA as the upper limit for the nitrate concentration in drinking water. At present the WHO limit is also 45 ppm of nitrate but the value of 22 ppm of nitrate has been set for EC countries. 

A1(N03)3 is completely soluble, so there would be three times the number of moles of nitrate ions present in the solution because... 

Therefore, the number of moles of nitrate ions in the original solution would be 0.16 x 3 = 0.48. 

The number of moles of nitrate ions needs to be brought up to 0.77 because the volume did not change (it remained at 0.45 liter). 

The solution begins with 0.48 mole of nitrate ions and must end up with 0.77 moles of nitrate ions therefore, the solution needs an additional 0.29 mole of nitrate ions ... 

Calcium nitrate, Ca(N03)2, produces 2 moles of nitrate ions in solution for each mole of solid calcium nitrate added to the solution. Therefore, because 0.29 mole of N03 is needed, you will need 0.29 / 2 = 0.15 mole of solid Ca(N03)2. 

H. Kato, A. Kudo, Photocatalytic reduction of nitrate ions over tantalate photocatalysts, Phys. Chem. Chem. Phys. 4 (2002) 2833-2838. 

Thorium oxide, has the highest melting point of the usual ceramic materials (3390°C). It is used to form ceramics, Th02, as the so-called meta-Th02, freshly prepared by low temperature decomposition of thorium oxalate it is fairly soluble in acids and tends (especially in the presence of nitrate ions) to form colloidal solutions which can be dried to form stable gels that can be sintered to give high-density ceramic bodies. 

A change in ionic adsorption in the presence of organic molecules was also observed by Parsons and Zobel. They found that in the presence of acetanilide in the inner layer, the surface concentration of specifically adsorbed phosphate ions decreases. In another work it was suggested that specific adsorption of nitrate ions is markedly reduced in the presence of thiourea in the solution. Thiourea alters the properties of the mercury electrode, affecting even the adsorption of iodides. ... 

The different molecular species present in a palladium nitrate solution can be easily identified by UV-visible spectroscopy (Fig. 13.2). Two absorption peaks are generally observed at A, = 285 nm and A = 378 nm, the latter being ascribed to free nitrate ions corresponding to the electronic transition from the a to the it state in the NOs ions, as observed in the case of an aqueous solution of NaNOs. The other absorption band at A = 285 nm is assigned to a d-d transition in the aquo complex Pd(H20)4 These UV-visible results show the noncomplexant behavior of nitrate ions toward palladium metallic centers. The palladium containing species in the starting solution is then the planar tetra-aquo complex Pd(H20)4 +. 

Niessen, R., Lenoir, D., and Boule. P. Phototransformation of phenol induced by excitation of nitrate ions, Chemosphere, 17(10) 1977-1984, 1988. 

Another important source for false-positive results in the use of the Griess reaction for the identification of explosives is the possible presence of nitrate ions, together with some accidental reducing substances. In this situation, the nitrate ions (NOs ) could be reduced to nitrite ions (NO2 ), giving a positive result in the Griess reaction. 

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