Chapter 9, Problem 81A

(a)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

The chemical formula of magnesium sulfide is $\text{MgS}$ . Since both Mg and S are divalent atoms, there is no need for subscripts.

Explanation of Solution

Magnesium sulfide is a binary ionic compound of magnesium and sulfur. Since both Mg and S are divalent atoms, there is no need for subscripts and hence the formula MgS.

(b)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

The chemical formula of sodium phosphite is ${\text{Na}}_{\text{2}}{\text{HPO}}_{\text{3}}$ .

Explanation of Solution

The name phosphite denotes ${\text{HPO}}_{\text{3}}{}^{2-}$ ions, which combine with sodium ions to form sodium phosphite. Hence the formula of the compound is ${\text{Na}}_{\text{2}}{\text{HPO}}_{\text{3}}$ .

(c)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

Barium hydroxide can be chemically represented as $\text{Ba}{\left(\text{OH}\right)}_{\text{2}}$ .

Explanation of Solution

The ionic compound barium hydroxide contains group two metal barium with two positive charges. So two hydroxide ions are needed to maintain electrical neutrality, hence the formula is $\text{Ba}{\left(\text{OH}\right)}_{\text{2}}$ .

(d)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

The chemical formula of copper (II) nitrite is $\text{Cu}{\left({\text{NO}}_{\text{2}}\right)}_{\text{2}}$ .

Explanation of Solution

The ionic compound copper nitrite consists of ${\text{Cu}}^{\text{2+}}$ ions and nitrite ions $\left({\text{NO}}_{\text{2}}{}^{-}\right)$ . Every copper ion combines with two nitrite ions to neutralize the charge. Hence the formula is $\text{Cu}{\left({\text{NO}}_{\text{2}}\right)}_{\text{2}}$ .

(e)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

The chemical formula of potassium sulfite is ${\text{K}}_{\text{2}}{\text{SO}}_{\text{3}}$ .

Explanation of Solution

The given ionic compound consists of potassium ions and sulfite ions $\left({\text{SO}}_3{}^{2-}\right)$ . Every sulfite ion combines with two potassium ions to neutralize the charge. Hence the formula is ${\text{K}}_{\text{2}}{\text{SO}}_{\text{3}}$ .

(f)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

Calcium carbonate can be chemically represented as ${\text{CaCO}}_{\text{3}}$ .

Explanation of Solution

Both calcium and carbonate are divalent ions, hence they simply combine to form calcium carbonate with the chemical formula ${\text{CaCO}}_{\text{3}}$ .

(g)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

The ionic compound sodium bromide can be chemically represented as NaBr.

Explanation of Solution

Sodium bromide is an ionic compound formed by the combination of metallic sodium and non-metal bromine. Both of them are monovalent, hence they simply combine to give NaBr.

(h)

Interpretation Introduction

Interpretation: The chemical formula of the given compound is to be determined.

Concept Introduction: Ionic compounds are named by writing the name of the metal ions followed by those of the anions. The name of an ionic compound ends in the suffix ‘-ide’ if it contains just two elements and in ‘-ate’ if it contains three or more elements.

Answer to Problem 81A

The chemical formula of the compound ferric sulfate is ${\text{Fe}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$ .

Explanation of Solution

If a metal ion exhibits more than one cation charge, the suffix ‘-ic’ is used to represent the greater charge while ‘-ous’ is used to denote a lower one. Iron usually exists in +2 and +3 states, here the suffix ‘ic’ represents ${\text{Fe}}^{\text{3+}}$ . It combines with sulfate ions to form ${\text{Fe}}_{\text{2}}{\left({\text{SO}}_{\text{4}}\right)}_{\text{3}}$ . The subscripts are written by interchanging the charges of ions.