Consider the formation of an alkaline earth metal halide MX ₂( s ) from its constituent elements. The standard enthalpy of formation of MX ₂( s ) is -600 ~kJ ~mol ⁻¹ . The enthalpy of sublimation of M ( s ) is 150 ~kJ ~mol ⁻¹ . The first and second ionization enthalpies of M ( g ) are 600 ~kJ ~mol ⁻¹ and 1200 ~kJ ~mol ⁻¹ , respectively. The bond dissociation enthalpy of X ₂( g ) is 200 ~kJ ~mol ⁻¹ and the electron ga

Step-by-step solution

The Born-Haber cycle for the formation of MX ₂( s ) from M ( s ) and X ₂( g ) involves the following steps: 1. Sublimation of M ( s ) to M ( g ) : H _ sub = 150 ~kJ ~mol ⁻¹ 2. Ionization of M ( g ) to M ²⁺( g ) : IE ₁ + IE ₂ = 600 + 1200 = 1800 ~kJ ~mol ⁻¹ 3. Dissociation of one mole of X ₂( g ) to 2 X ( g ) : H _ diss = 200 ~kJ ~mol ⁻¹ (Note: No 1 2 factor is needed because two moles of X are required for MX ₂ ) 4. Electron gain of 2 X ( g ) to 2 X ⁻( g ) : 2 H _ eg = 2 (-350) = -700 ~kJ ~mol ⁻¹ 5. Formation of th