Chapter 2, Problem 2.96P

(a)

Interpretation Introduction

Interpretation:

The formulas for ammonium and ammonia are to be determined.

Concept introduction:

Covalent bonds are formed by the sharing of electrons between two or more atoms. In covalent bonding, there is a mutual attraction between two nuclei and the two electrons that reside between them. The elements that engage in covalent bond formation are present at the rightmost corner of the periodic table. These elements are non-metals. The interaction between two non-metal elements leads to the formation of a covalent bond.

Answer to Problem 2.96P

The formula for ammonia is ${\text{NH}}_3$. The formula for ammonium is ${\text{NH}}_4^{+}$.

Explanation of Solution

Ammonia is a covalent compound in which three hydrogen atoms are covalently bonded to a nitrogen atom. It is denoted by the molecular formula ${\text{NH}}_3$.

The ammonium ion is a molecule of ammonia in which one hydrogen ion ${\text{H}}^{+}$ is added as follows:

${\text{NH}}_3+{\text{H}}^{+}\to {\text{NH}}_4^{+}$

The difference between ammonia and ammonium is, while the former is a neutral molecule, the latter is an ion with $+1$ charge.

Conclusion

The formula for ammonia is ${\text{NH}}_3$. The formula for ammonium is ${\text{NH}}_4^{+}$.

(b)

Interpretation Introduction

Interpretation:

The formulas for magnesium sulfide, magnesium sulfite, and magnesium sulfate are to be determined.

Concept introduction:

The general rules for naming ionic compounds are as follows:

1) In ionic compounds, the cations are named before the anions.

2) In binary ionic compounds, the name of the cation is the same as the name of the metal. The name of the anion includes the root name of the non-metal and a suffix $\text{-}ide$.

3) In polyatomic ions in which a non-metal is bonded to one or more oxygen atoms. In two oxoanions in the family, the ion with fewer oxygen atoms has the non-metal root name and a suffix $\text{-}ite$ added to it whereas the ion with more oxygen atoms has the non-metal root name and the suffix $\text{-}ate$ added to it.

Answer to Problem 2.96P

The formula for magnesium sulfide is $\text{MgS}$. The formulas for magnesium sulfite and magnesium sulfate are ${\text{MgSO}}_3$ and ${\text{MgSO}}_4$ respectively.

Explanation of Solution

Magnesium sulfide is a binary ionic compound. It is formed as follows:

${\text{Mg}}^{2+}+{\text{S}}^{2-}\to \text{MgS}$

The sulfide ion is represented by the formula ${\text{S}}^{2-}$. The $-2$ charge on the sulfide ion is balanced by a magnesium ion. Magnesium belongs to the $2\text{A}\left(2\right)$ group in the periodic table, therefore on losing two electrons the charge on the magnesium ion is $+2$. Therefore the formula for magnesium sulfide is $\text{MgS}$.

Sulfate and sulfite are polyatomic oxoanions. The charge on both sulfate and sulfite is $-2$ on each. In oxoanions, the ion with fewer oxygen atoms has the non-metal root name and a suffix $\text{-}ite$ added to it whereas the ion with more oxygen atoms has the non-metal root name and the suffix $\text{-}ate$ added to it. Therefore the formulas for sulfate and sulfite are ${\text{SO}}_4^{2-}$ and ${\text{SO}}_3^{2-}$ respectively.

The formation of magnesium sulfate and magnesium sulfite occur as follows:

${\text{Mg}}^{2+}+{\text{SO}}_4^{2-}\to {\text{MgSO}}_4$

${\text{Mg}}^{2+}+{\text{SO}}_3^{2-}\to {\text{MgSO}}_3$

The $-2$ charge on the sulfate and sulfite ions are balanced by a magnesium ion with $+2$ charge. Therefore the formulas for magnesium sulfate and magnesium sulfite are ${\text{MgSO}}_4$ and ${\text{MgSO}}_3$ respectively.

Conclusion

The formula for magnesium sulfide is $\text{MgS}$. The formulas for magnesium sulfite and magnesium sulfate are ${\text{MgSO}}_3$ and ${\text{MgSO}}_4$ respectively.

(c)

Interpretation Introduction

Interpretation:

The formulas for hydrochloric acid, chloric acid, and chlorous acid are to be determined.

Concept introduction:

The general formula for naming binary acids is,

$\text{Prefix }hydro\text{-}+\text{non-metal root}+\text{suffix -}ic+\text{acid}$

The general rules for naming the members of a family with four oxoanions are as follows:

1) The anion with the most number of oxygen atoms has the refix $per\text{-}$, the non-metal root and the suffix $\text{-}ate$.

2) The anion with one fewer oxygen atom has the non-metal root and the suffix $\text{-}ate$.

3) The anion with two fewer oxygen atoms has the non-metal root and the suffix $\text{-}ite$.

4) The anion with three fewer oxygen atoms has the prefix $hypo\text{-}$, the non-metal root, and the suffix $\text{-}ite$.

Answer to Problem 2.96P

The formula for hydrochloric acid is $\text{HCl}$. The formulas for chloric and chlorous acids are ${\text{HClO}}_3$ and ${\text{HClO}}_2$ respectively.

Explanation of Solution

Hydrochloric acid is a binary acid formed by the association of a hydrogen ion with $+1$ charge and chloride ion with $-1$ charge as follows:

${\text{H}}^{+}+{\text{Cl}}^{-}\to \text{HCl}$

Therefore the formula for hydrochloric acid is $\text{HCl}$.

The oxoanions of chlorine are ${\text{ClO}}^{-}$, ${\text{ClO}}_2^{-}$, ${\text{ClO}}_3^{-}$, ${\text{ClO}}_4^{-}$

The anion ${\text{ClO}}_4^{-}$ has the most number of oxygen atoms. Therefore it is the perchlorate ion. The anion ${\text{ClO}}_3^{-}$ has one fewer oxygen atom, therefore it is the chlorate ion. The anion ${\text{ClO}}_2^{-}$ is the chlorite ion and the anion ${\text{ClO}}^{-}$ is the hypochlorite ion.

In the ion chlorate, the root name chlor denotes the non-metal chlorine $\left(\text{Cl}\right)$. The formula for chlorate ion is ${\text{ClO}}_3^{-}$. On associating with a hydrogen ion with $+1$ charge, the formation of chloric acid occurs as follows:

${\text{ClO}}_3^{-}+{\text{H}}^{+}\to {\text{HClO}}_3$

The suffix $\text{-}ate$ in the anion chlorate is replaced by the suffix $\text{-}ic$

In the ion chlorite, the root name chlor denotes the non-metal chlorine $\left(\text{Cl}\right)$. The formula for chlorite ion is ${\text{ClO}}_2^{-}$. On associating with a hydrogen ion with $+1$ charge, the formation of chlorous acid occurs as follows:

${\text{ClO}}_2^{-}+{\text{H}}^{+}\to {\text{HClO}}_2$

The suffix $\text{-}ite$ in the anion chlorite is replaced by the suffix $\text{-}ous$.

Therefore the formulas for chloric and chlorous acids are ${\text{HClO}}_3$ and ${\text{HClO}}_2$ respectively.

Conclusion

The formula for hydrochloric acid is $\text{HCl}$. The formulas for chloric and chlorous acids are ${\text{HClO}}_3$ and ${\text{HClO}}_2$ respectively.

(d)

Interpretation Introduction

Interpretation:

The formulas for cuprous bromide and cupric bromide are to be determined.

Concept introduction:

The general rules for naming ionic compounds with different charges on the same metal are:

1) The root name of the metal is followed by the suffix $\text{-}ous$ for the ion with a lower charge.

2)The root name of the metal is followed by the suffix $\text{-}ic$ for the ion with a higher charge.

Answer to Problem 2.96P

The formulas for cuprous bromide and cupric bromide are $\text{CuBr}$ and ${\text{CuBr}}_2$ respectively.

Explanation of Solution

The element bromine belongs to the $7\text{A}\left(17\right)$ group in the periodic table. Therefore, an atom of bromine has the tendency to gain an electron to form a bromide ion as follows:

$\text{Br}+{\text{e}}^{-}\to {\text{Br}}^{-}$

The two ions formed by the copper element are ${\text{Cu}}^{+}$ and ${\text{Cu}}^{2+}$. The ${\text{Cu}}^{+}$ ion has one fewer charge on it. Therefore it is the cuprous ion. The ${\text{Cu}}^{2+}$ ion is the cupric ion.

To balance the $+1$ charge on the cuprous ion, one bromide ion with $-1$ charge combines with it to form the molecule of cuprous bromide as follows:

${\text{Cu}}^{+}+{\text{Br}}^{-}\to \text{CuBr}$

To balance the charge on the cupric ion, two bromide ions associate with one cupric ion to form the molecule of cupric bromide as follows:

${\text{Cu}}^{2+}+2{\text{Br}}^{-}\to {\text{CuBr}}_2$

Conclusion

The formulas for cuprous bromide and cupric bromide are $\text{CuBr}$ and ${\text{CuBr}}_2$ respectively.