Based on ion charges and relative ion sizes, rank these ionic compounds by their expected melting points.

Question

SrCl2

CsBr

RbCl

SrS

Answer 1

Melting point will be related to lattice energy. The greater the lattice energy, the higher the melting point because it will take more energy (heat) to break the lattice. Now, lattice energy is related to charge on the ions and the size of the ion. The greater the charge and the smaller the ion, the greater the lattice energy and hence the higher the melting point. The lattice energy has SrCl2 > SrS > RbCl > CsBr so melting point will be that SrCl2 has the highest melting point, followed by SrS then RbCl and finally CsBr