Sodium standard entropies

Sodium Chlorite. The standard enthalpy, Gibbs free energy of formation, and standard entropy for aqueous chlorite ions ate AH° = —66.5 kJ/mol ( — 15.9 kcal/mol), AG = 17.2 kJ/mol (4.1 kcal/mol), and S° = 0.1883 kJ/(molK) (0.045 kcal/(molK)), respectively (107). The thermal decomposition products of NaClO, in the 175—200°C temperature range ate sodium chlorate and sodium chloride (102,109) ... 

The conventional standard entropy of an aqueous cation may be calculated from the change in standard entropy for its formation and the standard entropies of the element and that of dihydrogen, as shown in the following example for the aqueous sodium ion. 

Q Calculate the conventional standard entropy of the aqueous sodium ion. given that the standard entropv of dihydrogen is + 130.7 J K mol-1. 

Q CalcLilalc llio eonvcnlional standard entropy of the aqueous sodium ioti, gi cn that the sttmdard entropv of dihydroueti is 130.7. 1 K mol ... 

Table 3.9 Standard Gibbs energy, enthalpy and entropy changes of solution for the sodium halides...

Using the data given below (all values are in kJ/mol) and Born-Haber cycles for the formation of both the hydride and the chloride of sodium, calculate the standard heats of formation in each case. Which type of compound is more stable Briefly discuss the principal reasons for the differences in stabilities as measured by the standard heat of formation. Would you expect differences in entropy of formation to change your conclusions ... 

The parent 7-oxanorbomane, 1, is commercially available. Its preparation starts with the catalytic hydrogenation of hydroquinone to generate a mixture of trans-and cfs-cyclohexane-l,4-diol [15-18]. cfs-Cyclohexane-l,4-diol can be isomerized into the more stable trans isomer with metallic sodium [17]. Dehydratation of the latter on A4 zeolites, on alumina [19], or over nickel-kieselguhr catalyst [20] provides 1. This reaction is exergonic (ArG° = ArH° — TArS° = -3.1 2.5 kcal/mol) at room temperature as its standard gas phase heat of reaction amounts to ArH° = -1-7.3 2.5 kcal/mol. A variation of entropy of reaction of ca. -1-35 eu is assumed for this fragmentation, what leads to —TArS° = 298(0.035) = — 10.4 kcal/mol. The standard gas phase heat of formation of frans-cyclohexane-1,4-diol (Scheme 1) is estimated from that of cyclohexanol (—69.0 2.0 kcal/mol) and the standard heat of oxidation of cyclohexane into cyclohexanol (—39.5 kcal/ mol) [21]. Chickos and Acree [22] give AfH°(l) = -43.4 0.5 kcal/mol (see also [23-25]). 

Both, enthalpy and entropy at standard conditions for chemical elements and compounds are tabularised [50], Using these values Jacquorie [261] calculated H and S at standard conditions for a sodium calcium silicate, a sodium borosilicate and a pure silica glass (Table 2.1). 

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