To calculate the lattice energy of NaCl, we can use the Born-Lande equation:Lattice Energy U = Madelung constant * charge of cation * charge of anion * electrostatic constant / distance between ions where:Madelung constant = 1.748Charge of Na+ cation = +1 in elementary charge units Charge of Cl- anion = -1 in elementary charge units Electrostatic constant k = 8.9875 10^9 Nm^2/C^2Distance between ions r = 236 pm = 236 10^-12 mNow, we can plug in the values into the equation:U = 1.748 * 1 * -1 * 8.9875 10^9 Nm^2/C^2 / 236 10^-12 m U = -1.748 * 8.9875 10^9 Nm^2/C^2 / 236 10^-12 m U = -1.571 10^10 Nm^2/C^2 / 2.36 10^-10 mU = -6.66 10^8 J/CSince the charges are in elementary charge units, we need to multiply the result by the elementary charge e to get the lattice energy in Joules:Elementary charge e = 1.602 10^-19 CLattice Energy U = -6.66 10^8 J/C * 1.602 10^-19 CLattice Energy U = -1.067 10^-10 JThe calculated lattice energy of NaCl is approximately -1.067 10^-10 Joules.