Solution-precipitation reactions

These differences in the physical properties of pelagic calcareous sediments at DSDP sites 504 and 505 are a result of the temperature difference between the two sites. A more rapid decrease in diagenetic potential is favored by increasing sediment temperature. The rates of the diagenetic solution-precipitation reactions are increased because of the higher temperature (Baker et al 1980), and the accompanying increased concentrations of ions involved in cementation (Mottl et... 

One common type of reaction that occnrs in aqneons solntion is the precipitation reaction, which results in the formation of an insoluble product, or precipitate. A precipitate is an insoluble solid that separates from the solution. Precipitation reactions usually involve ionic compounds. For example, when an aqneons solution of lead nitrate [Pb(N03)2l is added to an aqueous solution of sodinm iodide (Nal), a yellow precipitate of lead iodide (Pbl2) is formed ... 

There are also other methods such as spray pyrolysis and electrospray pyrolysis besides the above method [26]. To prepare nanoparticles by spray pyrolysis, a starting solution is prepared by dissolving, usually, the metal salt of the product in the solvent. The droplets atomized from a starting solution are introduced to furnace. Drying, evaporation of solvent, diffusion of solute, precipitation, reaction of precursor, and surrounding gas, pyrolysis may occur inside the furnace before the formation of product. It is similar to spray drying except the type of precursor. For this, colloidal particles are typically used as precursors. Some products prepared by spray pyrolysis are listed in Table 34.1. 

Primary batteries [1] having liquid electrolytes generally use a solution or a solution-precipitation reaction of an element at the anode and a displacement or insertion reaction at the cathode. Most secondary batteries use insertion reactions at a solid cathode and may also use insertion reactions at the anode. 

Some common elemental solution or solution-precipitation reactions are ... 

Three major t)q)es of chemical processes occur in aqueous solution precipitation reactions, acid-base reactions, and oxidation-reduction reactions. 

As we discussed in Chapter 7, many chemical reactions take place in aqueous solutions. Precipitation reactions, neutralization reactions, and gas evolution reactions, for example, all occur in aqueous solutions. Chapter 8 describes how we use the coefficients in chemical equations as conversion factors between moles of reactants and moles of products in stoichiometric calculations. These conversion factors are often used to determine, for example, the amount of product obtained in a chemical reaction based on a given amount of reactant or the amount of one reactant needed to completely react with a given amount of another reactant. The general solution map for these kinds of calculations is ... 

The reactions between C03 and Mg and C a are examples of precipitation reactions, reactions in which a solid or precipitate forms when we mix two solutions. Precipitation reactions are common in chemistry. As another example, consider potassium iodide and lead(ll) nitrate, which form colorless, strong electrolyte solutions when... 

Bratton The hydration of CaO is believed to occur by a solution-precipitation reaction ( through solution mechanism ). If this hydration process occurred, could the observed enhancement in the initial reaction be a result of better coverage of the silica grains by calcium ions ... 

Mix 1 g. of the nitro compound with 4 g, of sodium dichromate and 10 ml. of water in a 50 ml. flask, then attach a reflux condenser to the flask. Add slowly and with shaking 7 ml. of concentrated sulphuric acid. The reaction usually starts at once if it does not, heat the flask gently to initiate the reaction. When the heat of reaction subsides, boil the mixture, cautiously at first, under reflux for 20-30 minutes. Allow to cool, dilute with 30 ml. of water, and filter oflF the precipitated acid. Purify the crude acid by extraction with sodium carbonate solution, precipitation with dUute mineral acid, and recrystaUisation from hot water, benzene, etc. 

Aminothiazole is efficiently purified by treating an aqueous solution of 2-aminothiazole hydrochloride with H2SO4 at 25 to 105°C, filtering the precipitated reaction product and transforming it back to 2-aminothiazole... 

A precipitation reaction occurs when two or more soluble species combine to form an insoluble product that we call a precipitate. The most common precipitation reaction is a metathesis reaction, in which two soluble ionic compounds exchange parts. When a solution of lead nitrate is added to a solution of potassium chloride, for example, a precipitate of lead chloride forms. We usually write the balanced reaction as a net ionic equation, in which only the precipitate and those ions involved in the reaction are included. Thus, the precipitation of PbCl2 is written as... 

Solid Compounds. The tripositive actinide ions resemble tripositive lanthanide ions in their precipitation reactions (13,14,17,20,22). Tetrapositive actinide ions are similar in this respect to Ce . Thus the duorides and oxalates are insoluble in acid solution, and the nitrates, sulfates, perchlorates, and sulfides are all soluble. The tetrapositive actinide ions form insoluble iodates and various substituted arsenates even in rather strongly acid solution. The MO2 actinide ions can be precipitated as the potassium salt from strong carbonate solutions. In solutions containing a high concentration of sodium and acetate ions, the actinide ions form the insoluble crystalline salt NaM02(02CCH2)3. The hydroxides of all four ionic types are insoluble ... 

MetaUic ions are precipitated as their hydroxides from aqueous caustic solutions. The reactions of importance in chlor—alkali operations are removal of magnesium as Mg(OH)2 during primary purification and of other impurities for pollution control. Organic acids react with NaOH to form soluble salts. Saponification of esters to form the organic acid salt and an alcohol and internal coupling reactions involve NaOH, as exemplified by reaction with triglycerides to form soap and glycerol,... 

Most of the heavy-metal impurities present in 2inc salt solutions must be removed before the precipitation reaction, or these form insoluble colored sulfides that reduce the whiteness of the 2inc sulfide pigment. This end is usually achieved by the addition of 2inc metal which reduces most heavy-metal ions to their metallic form. The brightness of 2inc sulfide can be improved by the addition of a small amount of cobalt salts (ca 0.04% on a Co/Zn basis) (20). Barium sulfate [7727-43-7] formed in the first step is isolated and can be used as an extender. 

Transparent red iron oxide is composed mainly of hematite, a-Ee202, having primary particles about 10 nm. It is prepared by a precipitation reaction from a dilute solution of an iron salt at a temperature around 30°C, foUowed by a complete oxidation in the presence of some seeding additives,... 

Two blue pigments can be prepared in transparent form cyanide iron blue and cobalt aluminum blue. These pigments are used in achieving a blue shade of the metal effect pigments in metallic paints. Transparent cyanide iron blue is prepared by a precipitation reaction similar to the one used for the preparation of the opaque pigment, but considerably lower concentrations of solutions are used. It is produced by Degussa (Germany), Manox (U.K), and Dainichiseika (Japan). 

Among arsenic, bismuth, lead, antimony, and sulfur in the concentration range of 5—26 ppm, bismuth had the greatest unit effect (59). A decrease in the annealing temperature prior to cold deformation led to a decrease in the measured unit effectiveness, indicating that at low temperature bismuth is not in sohd solution. Lead lowered the recrystaUization temperature, provided that the samples were aimealed at 700°C or lower. A precipitation reaction between lead and sulfur was proposed (60). 

Note that the brackets, [ ], refer to the concentration of the species. K,p is the solubility product constant hence [Cu " ] and [OH] are equal to the molar concentrations of copper and hydroxyl ions, respectively. The K p is commonly used in determining suitable precipitation reactions for removal of ionic species from solution. In the same example, the pH for removal of copper to any specified concentration can be determined by substituting the molar concentration into the following equation ... 

After termination of the reaction by adding 200 ml of a 25% aqueous acetic acid solution, the reaction mixture was mixed with 5 liters of cold acetone to precipitate the reaction product. The precipitate was collected by filtration, washed with acetone, and dissolved in 500 ml of distilled water. The resulting aqueous solution was immediately adjusted to pH 6.0 and poured into a column containing 2 liters of CM-Sephadex C-25 (NH type) packed in 0.05 M aqueous ammonium chloride solution to adsorb bleomycins. 

Strategy First decide what cation and anion are present in each solution. Then write the formulas of the two possible precipitates, combining a cation of one solution with the anion of the other solution. Check Figure 4.3 to see if one or both of these compounds are insoluble. If so, a precipitation reaction occurs. 

The precipitation reaction that occurs when solutions of Na2C03 and CaCl2 are mixed (Figure 4.5) can be represented by a simple equation. To obtain that equation, consider the identity of the reactants and products ... 

Write a net ionic equation for any precipitation reaction that occurs when solutions of the following ionic compounds are mixed. 

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