Chapter 5, Problem 1ALQ

In some cases the Roman numeral in a name is the same as a subscript in the formula, and in some cases it is not. Provide an example (formula and name) for each of these cases. Explain why the Roman numeral is not necessarily the same as the subscript.

Interpretation Introduction

Interpretation:

To determine, in some cases the Roman numeral in a name is the same as a subscript in the formula and in some case it is not. Provide an example of each of these cases. Explain why the Roman numeral is not necessarily the same as the subscript

Concept introduction: The Roman numeral in the name of the compound does not represent the number of ions present in the compound but represents the charge on the ion present in the compound.

Answer to Problem 1ALQ

The example for the case when the Roman numerical in a name is the subscript in the formula:

Formula: ${\text{FeCl}}_3$ name: iron (III) chloride

Formula: ${\text{FeCl}}_2$ name: iron (II) chloride

The example for the case when the Roman numerical in a name is not the subscript in the formula:

Formula: ${\text{PbO}}_2$ name: lead (IV) oxide.

Explanation of Solution

The Roman numeral in the name of the compound does not represent the number of ions present in the compound but represents the charge on the ion thus; it is not necessarily the same as the subscript of the molecular formula.

The example for the case when the Roman numerical in a name is the subscript in the formula:

Formula: ${\text{FeCl}}_3$ name: iron (III) chloride

Formula: ${\text{FeCl}}_2$ name: iron (II) chloride

The example for the case when the Roman numerical in a name is not the subscript in the formula:

Formula: ${\text{PbO}}_2$ name: lead (IV) oxide.

Conclusion

Thus, Roman numeral are shown in name only for those metals which shows variable valences.