Chapter 7, Problem 89A

(a)

Interpretation Introduction

Interpretation: The compound with the strongest electrostatic forces between NaCl and CaO needs to be determined.

Concept Introduction: An electrostatic bond is formed when a positive charge ion combines with a negative charge ion. Here, a positive ion is formed when an atom loses electron/s and a negative ion is formed when an atom gains an electron.

Explanation of Solution

The electrostatic force is directly proportional to the charge on the ion. If the charge on the ion increases, the electrostatic force by which it is combined with the opposite charge ion increases. On comparing NaCl and CaO, the charge on Na and Cl ions is +1 and -1 respectively and on Ca and O ions are +2 and -2 respectively.

(b)

Interpretation Introduction

Interpretation: The given melting point of NaCl and CaO is $801{}^{\text{o}}\text{C}$ and $2614{}^{\text{o}}\text{C}$ respectively. Whether this data supports the reasoning for electrostatic force or not needs to be explained.

Concept Introduction: For any compound, if the electrostatic force is more, more energy will be required to break the bond.

Explanation of Solution

Since the charge on ions formed from CaO is more, it has the strongest electrostatic force. Due to strong electrostatic force, a large amount of energy is required to break the bond and it has a higher melting point than NaCl.