Salts That Yield Acidic Solutions

A salt consisting of the anion of a strong acid and the cation of a weak base yields an acidic solution because the cation acts as a weak acid, and the anion does not react. For example, NH4CI produces an acidic solution because the NH4 ion, the cation that forms from the weak base NH3, is a weak acid, and the CF ion, the anion of a strong acid, does not react  

As you saw earlier, small, highly charged metal ions make up another group of cations that yield H3O in solution. For example, Fe(N03)3 produces an acidic 

A third group of salts that yield H30 ions in solutions consists of cations of strong bases and anions of polyprotic acids that still have one or more ioniz-able protons. For example, NaH2P04 yields an acidic solution because Na, the cation of a strong base, does not react, while H2P04, the first anion of the weak polyprotic acid H3PO4, is also a weak acid  

NH4 (flty) -I- H20(/) NHafflg) -I- Fl30 (aq) [dissociation of weak acid] 

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Salts That Yield Neutral Solutions Salts That Yield Acidic Solutions Salts That Yield Basic Solutions Salts of Weakly Acidic Cations and Weakly Basic Anions... 

Acid-Base Properties of Salt Solutions Salts That Yield Neutral Solutions... 

Most salts are strong electrolytes that dissociate completely into ions in solution. The reaction of these ions with water, called salt hydrolysis, can produce acidic or basic solutions. In salt hydrolysis, the conjugate bases of weak acids yield basic solutions, and the conjugate acids of weak bases yield acidic solutions. 

Salts that yield a neutral solution consist of ions that do not react with water. Salts that yield an acidic solution contain an unreactive anion and a cation that releases a proton to water. Salts that yield a basic solution contain an unreactive cation and an anion that accepts a proton from water. If both cation and anion react with water, the ion that reacts to the greater extent (higher K) determines the acidity or basicity of the salt solution. 

Salts that yield an acidic solution contain an unreactive anion and a cation that releases a proton to water. 

Meihylamine hydrochloride method. Place 100 g. of 24 per cent, methyl-amine solution (6) in a tared 500 ml. flask and add concentrated hydrochloric acid (about 78 ml.) until the solution is acid to methyl red. Add water to bring the total weight to 250 g., then introduce lSO g. of urea, and boil the solution gently under reflux for two and three-quarter hours, and then vigorously for 15 minutes. Cool the solution to room temperature, dissolve 55 g. of 95 per cent, sodium nitrite in it, and cool to 0°. Prepare a mixture of 300 g. of crushed ice and 50 g. of concentrated sulphuric acid in a 1500 ml. beaker surrounded by a bath of ice and salt, and add the cold methylurea - nitrite solution slowly and with mechanical stirring and at such a rate (about 1 hour) that the temperature does not rise above 0°. It is recommended that the stem of the funnel containii the methylurea - nitrite solution dip below the surface of the acid solution. The nitrosomethylurea rises to the surface as a crystalline foamy precipitate. Filter at once at the pump, and drain well. Stir the crystals into a paste with about 50 ml. of cold water, suck as dry as possible, and dry in a vacuum desiccator to constant weight. The yield is 55 g. (5). 

In acid solution, the double bond of (203) is hydrogenated to the trans-fused sulfone (204). Presumably, this hydrogenation goes through a cis-fused intermediate that is rapidly epimerized to (204) under the acidic conditions of the reaction. Condensation of the sodium salt of 7,7-ethylenedioxy-3-oxooctanoate (205) with (204) produces (206). Cmde (206) is cyclized, hydroly2ed, and decarboxylated, producing the tricycHc compound (207). Hydrogenation of (207) followed by ketal hydrolysis and cyclization affords (208) in an overall yield of 35% from hydrindandione (203). 

Ghromium(II) Compounds. The Cr(II) salts of nonoxidizing mineral acids are prepared by the dissolution of pure electrolytic chromium metal ia a deoxygenated solution of the acid. It is also possible to prepare the simple hydrated salts by reduction of oxygen-free, aqueous Cr(III) solutions using Zn or Zn amalgam, or electrolyticaHy (2,7,12). These methods yield a solution of the blue Cr(H2 0)g cation. The isolated salts are hydrates that are isomorphous with and compounds. Examples are chromous sulfate heptahydrate [7789-05-17, CrSO 7H20, chromous chloride hexahydrate... 

The stirrer is started and there is added rapidly a cold sulfuric acid solution made by adding enough ice to 200 cc. of concentrated sulfuric acid (sp. g. 1.84) (Note 7) so that some of the ice is not melted. The stirring is continued for five or ten minutes or until the yellow lumps of the sodium salt disappear. The mixture is then extracted with three 600-cc. portions of benzene (Note 8). The benzene is destilled (Note g) from the extracts on a water bath and the residue is transferred to a special 2-I. Claisen flask (Org. Syn. 1, 40) and distilled under diminished pressure. The product boils at i3o-i32°/37 mm. or ii7-iig°/2g mm. A small high-boiling fraction is redistilled to yield 20-30 g. more of the ethyl acetopyruvate. The total yield is 480-520 g. (61-66 per cent of the theoretical amount). 

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