Potassium iodide reaction with lead nitrate

Lead tetraacetate is added in small quantities, with stirring, to an ice-cold suspension of 11 g. of ethyl 3-(D-arabino-tetrahydroxybutyl)-5-methyl 4-furoate in 100 ml. of benzene plus 40 ml. of glacial acetic acid. Addition is stopped when there is a positive reaction with potassium iodide-starch paper. The mixture is stirred for a further ten minutes, filtered, and the benzene solution washed twice with water. The benzene layer is then dried with anhydrous sodium sulfate, filtered, and the filtrate evaporated to dryness. The residue (6 g.) is mixed with a solution of 7.5 g. of sodium hydroxide plus 20 g. of silver nitrate in 40 ml. of water, and heated for 40 minutes on a steam bath. The aqueous solution is filtered, acidified to Congo Red while being cooled with ice, and the crystals formed are removed by filtration, washed with ice-cold water, and dried over phosphorus pentoxide in the vacuum desiccator yield, 2.2 g. After recrystallization from water, the product has m. p. 234r-235°. 

Fig. 7.5 Items from the RSCRDI involving the chemical reactions between aqueous solutions of lead(II) nitrate with potassium iodide and with sodium iodide...

The equations we ve been writing up to this point have all been molecular equations. That is, all the substances involved in reactions have been written using their full formulas as if they were molecules. In Section 4.1, for example, we wrote the precipitation reaction of lead(II) nitrate with potassium iodide to yield solid Pbl2 using only the parenthetical (aq) to indicate that the reaction takes place in aqueous solution. Nowhere was it indicated that ions are involved ... 

One example of a double displacement reaction is the reaction of lead nitrate with potassium iodide to form lead iodide and potassium nitrate ... 

To understand precipitation reactions, it is essential to work with the ionic species that exist in aqueous solution. For instance, mixing colorless solutions of lead(II) nitrate and potassium iodide causes a brilliant yellow solid to precipitate from the mixture (Figure 4-4t. To identity this yellow solid, we must examine the chemical species present in the solutions. 

Precipitation reactions are processes in which soluble reactants yield an insoluble solid product that drops out of the solution. Formation of this stable product removes material from the aqueous solution and provides the driving force for the reaction. Most precipitations take place when the anions and cations of two ionic compounds change partners. For example, an aqueous solution of lead(II) nitrate reacts with an aqueous solution of potassium iodide to yield an aqueous solution of potassium nitrate plus an insoluble yellow precipitate of lead iodide ... 

The equations you have been looking at up to this point have been known as molecular equations. They are called this because all of the substances are written as though they are molecules, even when they may not presently be in that state. For example, in the previous section, two substances we were discussing were lead (II) nitrate and potassium iodide. In the example that used the two substances, both were in an aqueous solution. When the two solutions were mixed, the reaction occurred and crystalline lead (II) iodide was formed. However, if you had taken the crystalline forms of each reactant, Pb(N03)2 and KI, and thrown them together, they would have sat there for an indefinite amount of time with little or no reaction occurring. The two materials need to be dissolved (or in a molten state) for the reaction to occur. In the equation for the reaction, though, the materials are written as though they were molecules ... 

From the balanced equation, you can see that it is necessary to have twice as many moles of potassium iodide as lead nitrate for the reaction to complete. What if you only had 1.5 moles of KI, and 1 mole of Pb(N03)2 Since the ratio of KI to Pb(N03)2 is 2-to-l, if you only have 1.5 moles of KI, you could only combine with 0.75 moles of Pb(N03)2. Therefore, you would have 0.25 moles of unreacted Pb(N03)2 left in the reaction vessel after all KI had reacted. In this example, KI was the limiting reactant. 

When you mix two aqueous ionic compounds together, there are two possible outcomes. Either the compounds will remain in solution without reacting, or one aqueous ionic compound will chemically react with the other. How can you predict which outcome will occur Figure 9.4 shows what happens when an aqueous solution of lead(II) nitrate is added to an aqueous solution of potassium iodide. As you can see, a yellow solid—a precipitate—is forming. This is a double displacement reaction. Recall, from Chapter 4, that a double displacement reaction is a chemical reaction that involves the exchange of ions to form two new compounds. It has the general equation... 

A solution of lead(ll) nitrate is reacted with a solution of potassium iodide. Write a molecular equation, complete ionic equation, and net ionic equation for this reaction. 

Calcium cyanide can be analyzed by titration with silver nitrate using potassium iodide indicator. Sulfide interfering in the reaction is removed by sodium carbonate-lead acetate solution. 

Suppl. 67). Laboratory fires have been reported, cansed by contact of moisture with a potassium bromate, malonic acid, and cerinm ammoninm nitrate mixtnre, setting a high exothermic reaction (Bartmess et al. 1998). Bromates ignite when mixed with concentrated mineral acids, lead acetate, or phospho-ninm iodide, PH4I. Finely divided mixtures of bromates with finely divided metals, phosphorus, sulfur, or metal sulfides can explode when heated or subjected to friction (Mellor 1946). 

Precipitation reactions are common in chemistry. Potassium iodide and lead nitrate, for example, both form colorless, strong electrolyte solutions when dissolved in water (see tiie solubility rules). When the two solutions are combined, however, a brilliant yellow precipitate forms (T Figure 7.8). We can describe this precipitation reaction with the chemical equation ... 

If an exchange reaction occurs, lead would react with iodide to form lead iodide, Pbl, and potassium would react with nitrate to form potassium nitrate, KNO3. 

Marchand and co-workers reported a synthetic route to TNAZ (18) involving a novel electrophilic addition of NO+ NO2 across the highly strained C(3)-N bond of 3-(bromomethyl)-l-azabicyclo[1.1.0]butane (21), the latter prepared as a nonisolatable intermediate from the reaction of the bromide salt of tris(bromomethyl)methylamine (20) with aqueous sodium hydroxide under reduced pressure. The product of this reaction, A-nitroso-3-bromomethyl-3-nitroazetidine (22), is formed in 10% yield but is also accompanied by A-nitroso-3-bromomethyl-3-hydroxyazetidine as a by-product. Isolation of (22) from this mixture, followed by treatment with a solution of nitric acid in trifluoroacetic anhydride, leads to nitrolysis of the ferf-butyl group and yields (23). Treatment of (23) with sodium bicarbonate and sodium iodide in DMSO leads to hydrolysis of the bromomethyl group and the formation of (24). The synthesis of TNAZ (18) is completed by deformylation of (24), followed by oxidative nitration, both processes achieved in one pot with an alkaline solution of sodium nitrite, potassium ferricyanide and sodium persulfate. This route to TNAZ gives a low overall yield and is not suitable for large scale manufacture. 

The chlorides, bromides, iodides, and cyanides are generally vigorously attacked by fluorine in the cold sulphides, nitrides, and phosphides are attacked in the cold or may be when warmed a little the oxides of the alkalies and alkaline earths are vigorously attacked with incandescence the other oxides usually require to be warmed. The sulphates usually require warming the nitrates generally resist attack even when warmed. The phosphates are more easily attacked than the sulphates. The carbonates of sodium, lithium, calcium, and lead are decomposed at ordinary temp, with incandescence, but potassium carbonate is not decomposed even at a dull red heat. Fluorine does not act on sodium bofate. Most of these reactions have been qualitatively studied by H. Moissan,15 and described in his monograph, Lefluor et ses composes (Paris, 1900). 

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