Question

The common oxidation number for an alkaline earth metal is +2. Using the Kapustinskii equation and Born-Haber cycles, show that CaCl is an exothermic compound, where CaCl may have NaCl structure. Use a suitable analogy to estimate an ionic radius for Ca. Use a radius for Ca. (rg and rca is 1.38 and 1.00 A, respectively.) suitable analogy to estimate an ionic 0.345 1.21 2 Z,n U To where En is the # of ions in the empirical formula, the constant 1.21 is in units of A MJ mol and the constant 0.345 is in units of A. lonic radius of Cl is 1.81 A The first ionization energy of Ca is 589 kJ/mol. Heat of sublimation of Ca is 176 kJ/mol. Bond energy of Cl2 (g) 244 kJ/mol. The electron affinity of Cl is -355 kJ/mol. Enthalpy of CaCl formation is -717 kJ/mol.

Answer 1

2.Enthalpy chenge tor the reaction

Cals g) f Cau (8) JmAgHce) 12ikm Cca) Cacg) I540m Ca ta91 AH=-134D. 6 KJ mul EA 349Tmol Aa HCa)LE, t4aH Ca) +ER +AHLE (176t 590t60.S349) Ksmal- 1342.6ksma -163.1 kJma(Negati ve siqn indicatea thet A4H am enother mit empsund) rai

2CaCl(s) ? Ca(s) + CaCl2(s)

Since the reaction given above is highly exothermic, it is proved that CaCl rapidly converts to CaCl2 making it almost the non-existace of CaCl.

AHH(Call +AH(ca)- 24Hca 79.80KImelt (143Kfme -469.6 KJmo