Question

Lattice energy of ionic compounds depend upon:
A. packing of ions only
B. charge and size of ions
C. charge on ion only
D. size of ions only

Answer 1

Hint:This question is asked from the topic of different enthalpies of formation. Lattice energy is basically an enthalpy of formation of one mole of an ionic compound. The lattice energy will be dependent on different factors.

Complete step by step answer:
According to the definition of lattice energy, it is the energy that must be supplied to one mole of an ionic crystal in order to separate it into gaseous ions in a vacuum via an endothermic process. Alternatively, it is the amount of energy released when an ionic solid is formed from its gaseous ionic constituents via an exothermic process. By the both definitions, it is directly related to the strength of the ionic bond between the ions of crystals. The major two factors which affect the lattice energy are the magnitude of charge of the ions in the lattice and the distance between the cation and anion.
The two ions are attached with the electrostatic force of attraction between them. The strength of electrostatic force of attraction is directly proportional to the charge on the ions. Therefore, greater the charge on the ions, greater will be the attraction and stronger will be the lattice.
 The distance between the ions is inversely proportional to the lattice energy. The greater the distance between the ions, the lower will be the electrostatic forces between them. Therefore, the lattice energy will be lower.
So, the lattice energy will depend on the charge of ions and size of the ions both.
Therefore, the correct option is B.



Note:The important point regarding the lattice energy is the lattice energy cannot be calculated directly. We can use the Born-Haber cycle to find out the lattice energy of a lattice. Lattice energy is expressed in terms of kilojoules per moles.