Answer to Question #77290 in General Chemistry for Sakshi

Question

The lattice enthalpies of NaCl, KCl and AgCl are - 787, - 717 and - 916 kJ mo1^-1, respectively. Based on these values, arrange them in increasing order of water solubility and justify your answer

Answer 1

AgCl < KCl < NaCl

All this compounds have the same crystal structure. The difference is that the potassium ion is larger than the sodium ion because the potassium ion has more electron shells. This increase in size means that the oppositely charged ions in KCl are further part than those in NaCl and therefore it takes more energy to break up the ionic bond in KCl which we see as a reduction in the water solubility. Technically the lattice energy in KCl is lower because of the larger size of the potassium ion. The cation Ag is in the side steppe and has the smallest lattice energy so its salt is almost insoluble in water.