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The following reaction can be written as the sum of two reactions, one of which

ID: 614410 • Letter: T

Question

The following reaction can be written as the sum of two reactions, one of which relates to ionization energy and one of which relates to electron affinity: Rb(g) + I(g)-->Rb+(g) + I-(g)

Explanation / Answer

2 Rb (s) + Cl2 (g) ----> 2 RbCl (s) Enthalpy of Formation of RbCl is -430.5 kJ / mole Enthalpy of Formation of 2 Mole of RbCl is -430.5 kJ / mole x 2 = -861 kJ ____ ( per 2 moles ) 2 Rb (s) ----> 2 Rb (g) ____ Sublimation Enthalpy of Sublimation for Rubidium is 86 kJ / mole Enthalpy of Sublimation for 2 Mole of Rubidium is 86 kJ / mole x 2 = 172 kJ ____ ( per 2 moles ) = H1 2 Rb (g) ----> 2 Rb+ (g) + 2 e- ____ Ionization Ionization Energy of Rubidium is 402 kJ / mole Enthalpy of Ionization of 2 Mole of Rubidium is 402 kJ / mole x 2 = 804 kJ ____ ( per 2 moles ) = H2 Cl2 (g) ----> 2 Cl (g) ____ Bond Dissociation Bond Dissociation Energy of Cl2 (g) is 243 kJ / mole Enthalpy of this Dissociation ( 1 Mole of Cl2 gas ) = 243 kJ ____ ( per 1 mole of Cl2 ; per 2 moles of Cl atoms ) = H3 2 Cl (g) + 2 e- ----> 2 Cl- (g) Electron Affinity of Chlorine is -349 kJ / mole Enthalpy of this reaction ( of 2 Mole of Chlorine ) is -349 kJ / mole x 2 = -698 kJ ____ ( per 2 moles of Cl- ) = H4 2 Rb+ (g) + 2 Cl- (g) ----> 2 RbCl (s) ____ Formation of Crystal Lattice from Ions Enthalpy of this reaction ( which is reverse of Crystal Lattice Breakdown ) = - ( Lattice Energy of RbCl / mole ) x 2 mole = - 2 x ( Lattice Energy of RbCl ) = H5 Enthalpy of Formation of 2 Mole of RbCl = H1 + H2 + H3 + H4 + H5 ( -861 ) = ( 172 ) + ( 804 ) + ( 243 ) + ( -698 ) + ( H5 ) -1382 = H5 Lattice Energy = ( -1382 ) / ( -2 ) = ( +691 )