Chapter 7, Problem 113A

Interpretation Introduction

(a)

Interpretation:

The solids that has higher melting point from the pair NaCl or CsCl needs to be determined.

Concept introduction:

Solids have tendency to maintain their structure because in solids intermolecular force of attraction is higher than liquids and gases. They have a fixed shape thus solids are rigid.

Answer to Problem 113A

NaCl have higher melting point than CsCl. 

Explanation of Solution

Na and Cs are group 1 elements. They can form +1 cation. Atomic size increases on moving down a group. In ions, as the size decreases intermolecular forces which hold the solid together increases. Atomic size of sodium is lower than caesium. Thus NaCl has higher melting point than CsCl. 

(b)

Interpretation Introduction

Interpretation:

The solids that has higher melting point from the pair Ag or Cu needs to be determined.

Concept introduction:

Solids have tendency to maintain their structure because in solids intermolecular force of attraction is higher than liquids and gases. They have a fixed shape thus solids are rigid.

Answer to Problem 113A

Cu have higher melting point than Ag. 

Explanation of Solution

Ag and Cu are group 11 elements. Both elements are a good conductor of electricity.  Atomic size increases on moving down a group. In ions, as the size decreases intermolecular forces which hold the solid together increases. Atomic size of copper (Cu) is lower than silver (Ag). Thus, Cu has a higher melting point than Ag. 

(c)

Interpretation Introduction

Interpretation:

The solids that has higher melting point from the pair ${\text{Na}}_{\text{2}}\text{O}$ or MgO needs to be determined.

Concept introduction:

Solids have tendency to maintain their structure because in solids intermolecular force of attraction is higher than liquids and gases. They have a fixed shape thus solids are rigid.

Answer to Problem 113A

MgO has higher melting point than ${\text{Na}}_{\text{2}}\text{O}$ . 

Explanation of Solution

Between charged species strength of intermolecular attraction is depends on the charge of the ions. +ve and –ve ions have a stronger attraction. Na can form +1 cation and Mg can form +2 cation. In MgO, magnesium (Mg) carries +2 charge and in ${\text{Na}}_{\text{2}}\text{O}$ sodium carries +1 charge. Thus MgO has a higher melting point than ${\text{Na}}_{\text{2}}\text{O}$ .