Ammonia aqueous-phase equilibrium

One extraction process used industrially on a large scale is the purification of sodium hydroxide for use in the manufacture of rayon. The sodium hydroxide produced by electrolysis typically contains 1% sodium chloride and 0.1% sodium chlorate as impurities. If a concentrated aqueous solution of sodium hydroxide is extracted with liquid ammonia, the NaCl and NaClOs are partitioned into the ammonia phase in preference over the aqueous phase. The heavier aqueous phase is added to the top of an extraction vessel filled with ammonia, and equilibrium is reached as droplets of it settle through the ammonia phase to the bottom. This procedure reduces impurity concentrations in the sodium hydroxide solution to about 0.08% NaCl and 0.0002% NaClOj. 

Nickel is extracted from alkaline ammonia solutions by LIX 64N, but its equilibrium constant is five orders of magnitude smaller than that of copper.8 Also, it forms ammonia complexes more extensively than copper, which enhances the selectivity of LIX 64N for copper over nickel. Under conditions of simultaneous extraction the parameters of the chemical-reaction model for each individual metal are able to predict the iwo-metal equilibria provided that the equilibrium distribution of species in the aqueous phase is taken into account. 

D-Arabinose 88 l-Deoxy-l,l-bis(ethylsulfonyl)-D-mannitol (1 g) (prepared by oxidation of D-mannose diethyl dithioacetal with peroxypropionic acid in dioxan) is made into a slurry with water (10 ml), and then concentrated aqueous ammonia solution (1 drop) is added. The sulfone dissolves rapidly and after 30 min the precipitated diethyl methylene disulfone is filtered off. The filtrate is extracted four times with chloroform (10-ml portions), and the aqueous phase is evaporated in a vacuum at 40°. The residue is treated with hot methanol (5 ml) and after being kept for 24 h at 4° affords / -D-arabinose (0.32 g, 86%), [a]D20 —102° (c 3.5 at equilibrium in water). 

So under atmospheric conditions practically all dissolved ammonia in clouds is in the form of ammonium ion. The aqueous-phase concentrations of [NH ] in equilibrium with 1 ppb of NH3(g) are shown in Figure 7.9. The partitioning of ammonia between the gas and aqueous phases inside a cloud can be calculated using (7.9) and the effective Henry s law coefficient for ammonia, // = Wnh, Ka [H+]/ATm. If the cloud pH is less than 5 practically all the available ammonia will be dissolved in cloudwater (Figure 7.10). 

FIGURE 7.10 Equilibrium fraction of total ammonia in the aqueous phase as a function of pH and cloud liquid water content at 298 K. 

Carbon Dioxide/Water Equilibrium 345 Sulfur Dioxide 348 Ammonia/Water Equilibrium 353 Nitric Acid/Water Equilibrium 355 Equilibrium of Other Important Atmospheric Gases Aqueous-Phase Reaction Rates 361 S(IV) to S(VI) Transformation and Sulfur Chemistry 363... 

Table I. Equilibrium (a) and kinetic (b) isotopic fractionation factors (a) of importance to nitrogen cycling in lakes (Collister Hayes, 1991). As a first approximation, an a value of, for example, 1.020 implies a difference in of ca. 20%o between the reactant and product. In the case of N2 gas dis.solution, therefore, differs by less than l%o between the gaseous and aqueous phases, whereas gaseous ammonia liberated during ammonia volatilisation will be ca. i4%o lighter than the aqueous ammonia.

Ammonia (NH,) is emitted primarily from animal shelters, cleaning detergents, and fertilizer production. Ammonia in the aqueous phase establishes equilibrium with NH4, which results in increased pH. NH, affects the atmospheric corrosion chemistry by partly neutralizing acidifying pollutants, forming particulate ammonium sulfate [(NH4),S04] and acid ammonium sulfates such as NH4HSO4 and (NH4)4H(S04),. 

In a packed column, operating at approximately atmospheric pressure and 295 K, a 10% ammonia-air mixture is scrubbed with water and the concentration of ammonia is reduced to 0.1%. If the whole of the resistance to mass transfer may be regarded as lying within a thin laminar film on the gas side of the gas-liquid interface, derive from first principles an expression for the rate of absorption at any position in the column. At some intermediate point where the ammonia concentration in the gas phase has been reduced to 5%. the partial pressure of ammonia in equilibrium with the aqueous solution is 660 N/nr and the transfer rate is ]0 3 kmol/m2s. What is the thickness of the hypothetical gas film if the diffusivity of ammonia in air is 0.24 cm2/s ... 

The solubility of gaseous weak electrolytes in aqueous solutions is encountered in many chemical and petrochemical processes. In comparison to vapory-liquid equilibria in non reacting systems the solubility of gaseous weak electrolytes like ammonia, carbondioxide, hydrogen sulfide and sulfur dioxide in water results not only from physical (vapor-liquid) equilibrium but also from chemical equilibrium in the liquid phase. 

With an aqueous fluid phase of high ionic strength, the problem of obtaining activity coefficients may be circumvented simply by using apparent equilibrium constants expressed in terms of concentrations. This procedure is recommended for hydro-metallurgical systems in which complexation reactions are important, e.g., in ammonia, chloride, or sulfate solutions. 

In the example with aniline, the aniline vapor was provided by the equilibrium vapor liquid aniline. Vapor-phase intercalation can be done with compounds that are gases at room temperature and ambient pressure. The most common gas used for intercalation reactions is ammonia. Ammonia intercalation can be accomplished by exposing a host to the vapor generated by a concentrated aqueous ammonia solution. This multi-component vapor containing NH3(g), IfeOQj),... 

The law of mass action is widely applicable. It correctly describes the equilibrium behavior of all chemical reaction systems whether they occur in solution or in the gas phase. Although, as we will see later, corrections for nonideal behavior must be applied in certain cases, such as for concentrated aqueous solutions and for gases at high pressures, the law of mass action provides a remarkably accurate description of all types of chemical equilibria. For example, consider again the ammonia synthesis reaction. At 500°C the value of K for this reaction is 6.0 X 10 2 F2/mol2. Whenever N2, H2, and NH3 are mixed together at this temperature, the system will always come to an equilibrium position such that... 

An aqueous ammonia solution is in equilibrium with a vapor phase in a dosed system at 160 F and i atm. The liquid phase accounts for 95% of the total mass of the system contents. Use Figure 8.5-2 to determine the weight percent of NH3 in each phase and the enthalpy of the system per unit mass of the system contents. 

A number of different solid phases can precipitate from a solution of ammonia and carbon dioxide in water. As an example, the equilibrium of ammonium bicarbonate with an aqueous solution is written in the form (13) ... 

As the (NH4)2S04 in the particles increases compared to the ammonium nitrate, the parameter Y decreases and the equilibrium product of ammonia and nitric acid decreases. The additional ammonium and sulfate ions make the aqueous solution a more favorable environment for ammonium nitrate, shifting its partitioning toward the particulate phase. Therefore, addition of ammonium sulfate to aqueous aerosol particles will tend to increase the concentration of ammonium nitrate in the particulate phase, and, vice versa, reductions of ammonium sulfate can lead to decreases of ammonium nitrate for aqueous aerosol. 

Competition between sulfate and nitrate for the available ammonia results in rather complicated system behavior. Addition of ammonium sulfate to solutions containing aqueous ammonium nitrate lowers the ammonia-nitric acid vapor pressure product in equilibrium with the aerosol phase (Figure 9.21). In Figure 9.21, Y is the ionic strength fraction of ammonium sulfate and is calculated as... 

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