Salt solutions cation reaction with water

In the case of trivalent and tetravalent ions most, if not all, of the cationic species undergo complex reactions with water to form polynuclear species. A good example of this behaviour occurs with the ions formed from aluminium salts. At pH values less than about 3.5, when the salts are dissolved in water the prevalent species in solution is the AP" " ion. However, between about pH 3.5 and... 

The acidic ammonium chloride solution is an example of the second category of salts, where the NH4 cation is the conjugate acid of the weak base NH3, and the Cl anion is the conjugate base of the strong acid HCl. The hydrolysis reaction is given in Equation 9.47, where H30 is used to emphasize the reaction with water ... 

The variation in pH values can be accounted for by examining the ions formed when each of these salts dissociates. If the ions formed are from weak acids or bases, they react chemically with the water molecules, and the pH of the solution will have a value other than 7. A reaction between water molecules and ions of a dissolved salt is hydrolysis. If the anions react with water, the process is anion hydrolysis and results in a more basic solution. If the cations react with water molecules, the process is cation hydrolysis and results in a more acidic solution. 

J.12 C6HsNH3C1 is a chloride salt with an acidic cation, (a) If 50.0 g of C6H5NH3C1 is dissolved in water to make 150.0 mL of solution, what is the initial molarity of the cation (b) Write the chemical equation for the proton transfer reaction of the cation with water. Identify the acid and the base in this reaction. 

J.I3 Na As04 is a salt of a weak base that can accept more than one proton, (a) Write the chemical equations for the sequential proton transfer reactions of the anion with water. Identify the acid and the base in each reaction, (b) If 35.0 g of Na3As04 is dissolved in water to make 250.0 ml. of solution, how many moles of sodium cations are in the solution ... 

To determine whether the solution of a salt will be acidic, basic, or neutral, we must consider both the cation and the anion. First we examine the anion to see whether it is the conjugate base of a weak acid. If the anion is neither acidic nor basic, we examine the cation to see whether it is an acidic metal ion or the conjugate acid of a weak base. If one ion is an acid and the other a base, as in NH4F, then the pH is affected by the reactions of both ions with water and both equilibria must be considered, as in Section 10.19. 

As a measure of their thermodynamic stability, the pAfR+ values for the carbocation salts were determined spectrophotometrically in a buffer solution prepared in aqueous solution of acetonitrile. The KR+ scale is defined by the equilibrium constant for the reaction of a carbocation with water molecule (/CR+ = [R0H][H30+]/[R+]). Therefore, the larger p/CR+ index indicates higher stability for the carbocation. However, the neutralization of these cations was not completely reversible. This is attributable to instability of the neutralized products. The instability of the neutralized products should arise from production of unstable polyolefinic substructure by attack of the base at the aromatic core. 

When a salt is dissolved in water, the metal ions, especially transition metal ions, form a complex ion with water molecules and/or other species. A complex ion is composed of a metal ion bonded to two or more molecules or ions called ligands. These are Lewis acid-base reactions. For example, suppose Cr(N03)3 is dissolved in water. The Cr3+ cation attracts water molecules to form the complex ion Cr(H20)63+. In this complex ion, water acts as the ligand. If ammonia is added to this solution, the ammonia can displace the water molecules from the complex ... 

If a salt contains the cation of a strong base and the anion of a strong acid, neither ion reacts with water. Therefore, the solution has a pH of 7. Sodium chloride is an example of such a salt. It is formed by the reaction of sodium hydroxide (a strong base) and hydrochloric acid (a strong acid). Salts of strong bases and strong acids dissolve in water and form neutral solutions. 

With the knowledge that 14 can activate aldehydes in 1, the role of 1 in the reaction was explored further. Specifically, the relative rates of C—H bond activation and guest ejection, and the possibility of ion association with 1, were investigated. The hydrophobic nature of 14 could allow for ion association on the exterior of 1, which would be both cn t h al pi cal I y favorable due to the cation-it interaction, and entropically favorable due to the partial desolvation of 14. To explore these questions, 14 was irreversibly trapped in solution by a large phosphine, which coordinates to the iridium complex and thereby inhibits encapsulation. Two different trapping phosphines were used. The first, triphenylphosphine tris-sulfonate sodium salt (TPPTS), is a trianionic water-soluble phosphine and should not be able to approach the highly anionic 1, thereby only trapping the iridium complex that has diffused away from 1. The second phosphine, l,3,5-triaza-7-phosphaadamantane (PTA), is a water-soluble neutral phosphine that should be able to intercept an ion-associated iridium complex. 

Any ionic solid, such as ammonium chloride, is called a salt. In a formal sense, a salt can be thought of as the product of an acid-base reaction. When an acid and base react, they are said to neutralize each other. Most salts containing cations and anions with a single positive and negative charge are strong electrolytes—they dissociate nearly completely into ions in dilute aqueous solution. Thus, ammonium chloride gives NH and Cl- in water ... 

Related ammonium salts derived from amines, such as [CH3NH3]C1, [(CH3)2NH2]C1, and [(CH3)3NH]C1, also give acidic solutions because they too have cations with at least one dissociable proton. The pH of a solution that contains an acidic cation can be calculated by the standard procedure outlined in Figure 15.7. For a 0.10 M NH4C1 solution, the pH is 5.12. Although the reaction of a cation or anion of a salt with water to produce H30+ or OH - ions is sometimes called a salt hydrolysis reaction, there is no fundamental difference between a salt hydrolysis reaction and any other Bronsted-Lowry acid-base reaction. 

This reaction is an dehydration acid-catalyzed.12 The hexaaquocop-per cation behaves as a weak cationic acid in copper-salt solution.13 Protonation of the hydroxy group produces an oxonium ion that decomposes unimolecularly into carbocation 21 and water. Water is removed from the reaction equilibrium by means of a water-separating device. Carbocation 21 eliminates an -proton with formation of the energetically favorable conjugated diene 9. 

Besides the effect of the electrode materials discussed above, each nonaqueous solution has its own inherent electrochemical stability which relates to the possible oxidation and reduction processes of the solvent,the salts, and contaminants that may be unavoidably present in polar aprotic solutions. These may include trace water, oxygen, CO, C02 protic precursor of the solvent, peroxides, etc. All of these substances, even in trace amounts, may influence the stability of these systems and, hence, their electrochemical windows. Possible electroreactions of a variety of solvents, salts, and additives are described and discussed in detail in Chapter 3. However, these reactions may depend very strongly on the cation of the electrolyte. The type of cation present determines both the thermodynamics and kinetics of the reduction processes in polar aprotic systems [59], In addition, the solubility product of solvent/salt anion/contaminant reduction products that are anions or anion radicals, with the cation, determine the possibility of surface film formation, electrode passivation, etc. For instance, as discussed in Chapter 4, the reduction of solvents such as ethers, esters, and alkyl carbonates differs considerably in Li or in tetraalkyl ammonium salt solutions [6], In the presence of the former cation, the above solvents are reduced to insoluble Li salts that passivate the electrodes due to the formation of stable surface layers. However, when the cation is TBA, all the reduction products of the above solvents are soluble. 

From this you can see that the cation from the salt comes from the base and the anion comes from the acid. Salts can act as Bronsted-Lowry acids or bases to produce solutions that are acidic or basic. The salts react with water in a reaction known as hydrolysis to yield either a conjugate acid and a hydroxide ion or a conjugate base and a hydrogen (hydronium) ion. If you know the origins of the components of a salt, you can make some predictions about the pH of the solution formed from a hydrolysis of a salt ion. 

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