Hydrogen with metals, thermochemical

A typical reaction of aldehydes and ketones is addition to the C—O ji bond. Examples of addition reagents are H2 (resulting in reduction to the corresponding alcohol), ROH (to give a hemiacetal or hemiketal) and RM (yielding a metal alkoxide). Only the hydrogenation reaction produces an addition product for which there is any useful quantity of thermochemical data, however. Equation 34 represents an overall reaction of the carbonyl compound with a (hypothetical) reagent XY, an equation which includes any reaction, subsequent to an initial addition reaction, to form products for which there are sufficient data. 

Figure 8. Temperature dependence of the equilibrium constant, Kp = p(HtO)/ p(Ht) for the reduction of several metal oxides often present in Tokamak walls. The Kp values are calculated from thermochemical data listed in Ref. 51. The reduction curve for NiO, the most prevalent metal oxide on Inconel alloys, lies above the FeO curve, and thus is more easily reduced in hydrogen than the oxides shown. (Reproduced, with permission, from Ref. 37. Copyright 1980, North-...

Hydrogen production by a 2-step water splitting thermochemical cycle can be based on metal oxides redox pairs. A two-step, water-split-ting cycle, based on metal oxides redox pairs bypasses the separation hurdle. Multi-step thermochemical cycles can allow the use of more moderate operating temperatures, but their efficiency is still limited by the irreversibility associated with heat transfer and product separation. 

What type of compounds will be covered in this overview. Strictly, only compounds which have at least one metal-carbon bond (with the exception of metal carbides) are called organometaiiic. However, this definition was not adopted in this chapter because many families of compounds that are relevant in organometaiiic chemistry would not be included (e.g., alkoxides). By metal we mean any element from groups 1 (except hydrogen), 2, 3 (including lanthanides and actinides), 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 (except boron), 14 (except carbon and silicon), and 15 (antimony and bismuth only). Most of the available thermochemical data for all these species are freely available in a single on-line database the NIST Chemistry WebBook Unless stated otherwise, all the data included in this chapter were quoted from that reference. 

When 1 mol of iron metal reacts with hydrochloric acid at constant temperature and pressure to produce hydrogen gas and aqueous iron(II) chloride, 89.1 kJ of heat evolves. Write a thermochemical equation for this reaction. 

---