Question

If $N{{a}^{+}}$ ion is larger than $M{{g}^{2+}}$ ion and ${{S}^{2-}}$ ion is larger than $Cl^-$ ion, which of the following will be stable soluble in water?

• A. Sodium chloride
• B. Sodium sulphide
• C. Magnesium chloride
• D. Magnesium sulphide

Answer 1

Answer: (D)

Magnesium sulphide

Answer 2

The lattice energy of a salt gives a rough indication of the solubility of the salt in water because it reflects the energy needed to separate the positive and negative ions in a salt. Sodium and potassium salts are soluble in water because they have relatively small lattice energies. Magnesium and aluminum salts are often much less soluble because it takes more energy to separate the positive and negative ions in these salts.