Hydrides chemical properties

Mendeleef drew up a table of elements considering the chemical properties, notably the valencies, of the elements as exhibited in their oxides and hydrides. A part of Mendeleefs table is shown in Figure 1.2 -note that he divided the elements into vertical columns called groups and into horizontal rows called periods or series. Most of the groups were further divided into sub-groups, for example Groups... 

Zirconium i dride. Zirconium hydride [7704-99-6] ZrH2, is a britde, metaUic-gray soHd that is stable in air and water, and has a density of 5.6 g/cm. The chemical properties of ZrH2 closely resemble those of titanium hydride. Thermal decomposition in vacuum (1 mPa (7.5 x 10 //mHg)) begins at 300°C and is nearly complete at 500—700°C. It is prepared in the same manner as T1H2. 

Greater selectivity in purification can often be achieved by making use of differences in chemical properties between the substance to be purified and the contaminants. Unwanted metal ions may be removed by precipitation in the presence of a collector (see p. 54). Sodium borohydride and other metal hydrides transform organic peroxides and carbonyl-containing impurities such as aldehydes and ketones in alcohols and ethers. Many classes of organic chemicals can be purified by conversion into suitable derivatives, followed by regeneration. This chapter describes relevant procedures. 

The compound sodium hydride, formed in reaction (29), is a crystalline compound with physical properties similar to those of sodium chloride. The chemical properties are very different, however. Whereas sodium burns readily in chlorine, it reacts with hydrogen only on heating to about 300°C. While sodium chloride is a stable substance that dissolves in water to form Na+(aqJ and CV(aq), the alkali hydrides bum in air and some of them ignite spontaneously. In contact with water, a vigorous reaction occurs, releasing hydrogen ... 

In order to fully understand the electrochemical behaviour of AB, hydrides, a knowledge of their chemical properties is required. Van Vucht et al. [25] were the first to prepare LaNi5 hydride and it is arguably the most thoroughly investigated H—storage compound. It reacts rapidly with hydrogen at room temperature at a pressure of several atmospheres above the equilibrium plateau pressure. PC isotherms for this system are shown in Fig. 3. 

Let us add here that despite the general similarities of selenium and sulfur in their chemical properties, the chemistry of selenium differs from that of sulfur in two important aspects their oxoanions are not similarly reduced, and their hydrides have different acid strengths. For example, Se(-HlV) tends to undergo reduction to Se(-II), whereas S(-hIV) tends to undergo oxidation. This difference is evidenced by the ability of selenous acid to oxidize sulftirous acid ... 

Sodium aluminate, 2 345t, 358-359 analysis, 2 275-276 economic aspects, 2 275 health and safety factors, 2 276 manufacture, 2 274-275 neutralization, 2 424 physical and chemical properties of, 2 273-274 uses of, 2 276-277 in water treatment, 26 111 Sodium aluminosilicate gels, synthetic zeolites prepared from, 16 831t Sodium aluminosilicates, 12 578 Sodium aluminum hydride, 13 621, 623-624... 

Hydrocarbons and hydrogen halides are omitted since they will be dealt with elsewhere.) The chemical properties of most of these hydrides are rather well known, but this cannot be asserted for their decomposition kinetics. Some of them are very stable (H20, HF, NH3) while others decompose easily at room temperature (TeH2, PbH4). A study of the homogeneous decomposition has only been undertaken for those elements inside the frame in the Table. The pyrolyses of the others have either been found to proceed heterogeneously or the kinetics is unknown. 

Saita, T. Toshima, S. Tanada, T. AMyama, Hydrogen storage property of MgH synthesized by hydriding chemical vapor deposition, J. Alloys Compd. 446-447 (2007) 80- 3. 

Many other fuels such as soot, turf, corkmeal, powdered anthracite, woodmeal, carbene (polymerized acetylene), calcium hydride, and spongy aluminum have been tried. Physical and chemical properties of many LOX fuels are given by Howell et al (Ref 3) and O Neil Van Fleet (Ref 5a)... 

As shown in Eqs. (17) and (18), the isolated formyls 19 and 24 are capable of reducing aldehydes and ketones (37, 38, 42. 47, 66). Thus there is no doubt that hydride transfer is an intrinsic chemical property of anionic formyl complexes. One reaction of a neutral formyl complex with an aldehyde has been reported addition of benzaldehyde to (i7-C5H5)Re(NO)(CO)(CHO) (38) yields the alkoxycarbonyl complex (i7-C5H5)Re(NO)(CO)(C02CH2C6Hs) (62). This transformation, which appears to require catalysis by adventitious acid, can be viewed as occurring via attack of initially formed benzyl alcohol upon the intermediate carbonyl cation [(i -C5H5)Re(NO)(CO)2]+. 

The chemical properties of lithium hydride, methane, and hydrogen fluoride are in accord with the above formulations. Thus, when the bond to the hydrogen is broken, we might expect it to break in the senseLi Hefor... 

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