Cesium with water, reaction

Figure 1. Enlargement of a typical oscilloscope trace reaction of cesium with water in ethylenediamine.

Earlier work (6) using this method yielded a second-order rate constant of 24.7 1.5 M""1 sec."1 for the reaction of dilute solutions of cesium with water in ethylenediamine. On the basis of optical absorption spectra (7) and other evidence (8, II), it was assumed that this reaction was that of the solvated electron as well as loosely bound electrostatic aggregates of electrons and cations with water. This permitted correlation with the results of aqueous radiation chemistry. 

Both sodium and cesium react with water. Predict the products of the reactions of sodium and cesium with water. Write balanced equations for both reactions. 

From Equations 7.18 and 7.16, we predict the reactions of cesium with water and hydrogen to proceed as follows ... 

Cesium reacts with water in ways similar to potassium and rubidium metals. In addition to hydrogen, it forms what is known as superoxides, which are identified with the general formula CsO When these superoxides react with carbon dioxide, they release oxygen gas, which makes this reaction useful for self-contained breathing devices used by firemen and others exposed to toxic environments. 

Graft copolymers were prepared by polymerizing ethylene oxide onto the PVN polyradical anion (10), The latter was obtained by reaction of PVN with cesium in tetrahydrofuran solution. The copolymers were extracted with water to remove the PEO homopolymer which was formed as a byproduct. Experimental details and evidence for bond formation between ethylene oxide and the aromatic moiety were presented elsewhere (//). 

Rate studies of the reaction between cesium and water in ethylenediamine, using the stopped-flow technique, have been extended to all alkali metals. The earlier rate constant (k — 20 NT1 sec.-1) and, in some cases, a slower second-order process (k — 7 Af"1 sec.-1) have been observed. This is consistent with optical absorption data and agrees with recent results obtained in aqueous pulsed-radiolysis systems. Preliminary studies of the reaction rate of the solvated electron in ethylenediamine with other electron acceptors have been made. The rate constant for the reaction with ethylene-diammonium ions is about 105 NCl sec.-1 Reactions with methanol and with ethanol show rates similar to those with water. In addition, however, the presence of a strongly absorbing intermediate is indicated, which warrants more detailed examination. 

The reactions of all the alkali metals with water, of cesium and rubidium with methanol, of cesium with ethanol, and of cesium with HC1 and with NH4Br have been examined. Figure 1 shows a typical oscilloscope trace, and Figure 2 shows a plot of log absorbance vs. time for this trace. The reaction is pseudo-first-order in metal (since solute concentration is ten or more times greater than metal concentration), and the overall rate constants and their order in solute are obtained by varying solute concentration. 

Methanol. Rubidium reacted with one methanol concentration, and two runs were made with cesium using several concentrations of methanol. While reaction times were comparable to those observed in the water reactions, several marked differences were apparent. In some cases two rates were observed, but the constants were not reproducible. More striking was the fact that the shapes of the traces themselves differed from picture to picture, and with dilute solutions seemed to indicate that an absorbing intermediate was formed. For these reasons we do not report any rate constants at this time. 

Reaction times of 5 days produced no detectable (by SEM) cesium-containing phases. However, after treating the minerals with water at 200 C for 14 days in the absence of cesium, then adding the appropriate amount of CsCl, we observed cesium aluminosilicate crystals within 42 hours of further hydrothermal reaction. 

Cesium is a very reactive metal. It combines readily with oxygen in the air and reacts violently with water. In the reaction with water, hydrogen gas is released. Hydrogen gas ignites immediately as a result of the heat given off by the reaction. 

The high reactivities of the alkali metals are illustrated by their vigorous reactions with water. Lithium reacts readily sodium reacts so vigorously that the hydrogen gas it forms may ignite and potassium, rubidium, and cesium cause the H2 to burst into flames when... 

Table 14 contains the rate constants for the reactions of solvated electrons with water and alcohols in different media. It is evident that reduction of proton donors in fact proceeds very slowly. Also, water reacts slowly with methylamine solutions of cesium and sodium... 

The alkali metals—lithium, sodium, potassium, rubidium, cesium, and francium—make up Group 1 of the periodic table. These metals are highly reactive. For example, if potassium is dropped into water, the reaction will transform potassium into potassium hydroxide and hydrogen gas. When these metals react with water, hydrogen gas is given off, and heat—often hot enough to create flames—can appear. The heat produced by the interaction is enough to liquefy the metal. 

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