Question

Answer the following questions without using data from the text or slides. You should only need a periodic table and Coulomb's Law: P.E. = (k Q₁Q₂)/d

a) Two ionic compounds have formulas of AO and BO, where O is oxide ion and A and B are different metallic ions. The lattice energies of the two compounds are: AO = -3222 kJ/mol and BO = -3800 kJ/mol. Which of the two cations has the larger ionic radius?

b) Arrange the compounds CsCl, NaCl, MgCl₂ and RbCl in order of increasing lattice energy. Remember, lattice energies are negative quantities and the more negative the value the stronger the attraction of the positive and negative ions.

Answer 1

FUHLUW (a) dattece energies of two compounds are given as Aoe -3232 kJ/mol A, B - Metallie ons Bos -3800 kilmu! 0 + Oxide zon. te, -ve Cregateve) segon indicate an exothermic reaction Also, size of the ton and Lattlee energy are cinversely related. That means, desser the lattice energy, greater the stue of Ton (given by conte radius) and the opposite is also true In to and Bo to has lesser Lattice energy . The metallic Too A has larger ronic radius- (6) Given compounds are Coce , NaCl, MgCl₂ and Rbce. charge of ton increases, the lattice energy increases Also, as some of ton increases, lattice energy decreases. So, we have the metallic Toos as Cst, Nat, mgt, eht Among the given rons, Na, Rb, Cs are placed from top to bottom respectively in Group-1 of Periodic table. So, the increase in stee of the above three would be cs4Rb4a. -> decreasing Sthe 4ton, Increase in (LE)

ordee s. The Lattice energy for cs, Rb and Mã tons can for Cs, Rb be given as Cat ZRb Anat And Mall & gt2 has a greater charge compariticely. So, for eact, NaCl, MgCl and the the decreasing order of Lattle energy will bes mguly > Na Cl > ebal > CsCl. Greater the stue of Ton, lesser the lattice energy. Greater the charge of ton greated the Kattece energy