Calculate the lattice energy (kj/mol) of the hypothetical ionic compound mx from the information given below. ie1(m) = 538 kj/molm(s) => m(g) δho = 74.4 kj/molδhof(mx) = -169.7 kj/molx2(g) => 2x(g) δh = 157 kjea (x) = -366 kj/molie1 (x) = 271 kj/mol

The correct answer is -494.6 kJ/mol

Explanation:

Find enclosed the Born Haber cycle for MX. The solid compound M (M(s)) is sublimated to M(g) and then it is ionizated to M⁺. The gaseous compound X₂(g) is first dissociated to its atoms in gaseous phase X(g) and then it is ionizated to give X⁻(g). Lattice energy (LE) is the energy required to form 1 mol of MX(s) from its ions in gaseous phase.

From the cycle, we have:

ΔHºf= ΔHsub + IE + ΔHdis + EA + LE

⇒LE= ΔHºf - ΔHsub - IE - 1/2 ΔHdis - EA

  LE= -169.7 kJ/mol - (74.4 kJ/mol) - (538 kJ/mol) - 1/2 (157 kJ/mol) - (-366 kJ/mol)

  LE= -494.6 kJ/mol