Chapter 7, Problem 7E

Interpretation Introduction

(a)

Interpretation:

The formula mass of lithium chloride is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass of lithium chloride is $\text{42}\text{.39}\text{u}$.

Explanation of Solution

The chemical formula for lithium chloride is $\text{LiCl}$. The atomic mass of lithium and chlorine is $\text{6}\text{.941}\text{u}$ and $\text{35}\text{.45}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}\text{LiCl}=\text{Atomic}\text{mass}\text{of}\text{Li}+\text{Atomic}\text{mass}\text{of}\text{Cl}$

Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}\text{LiCl}& =& \text{Atomic}\text{mass}\text{of}\text{Li}+\text{Atomic}\text{mass}\text{of}\text{Cl}\\ & =& \text{6}\text{.941}\text{u}+\text{35}\text{.45}\text{u}\\ & =& \text{42}\text{.39}\text{u}\end{array}$

Thus, the formula mass of lithium chloride is $\text{42}\text{.39}\text{u}$.

Conclusion

The formula mass of lithium chloride is $\text{42}\text{.39}\text{u}$.

Interpretation Introduction

(b)

Interpretation:

The formula mass of aluminum carbonate is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass of aluminum carbonate is $\text{233}\text{.99}\text{u}$.

Explanation of Solution

The chemical formula for aluminum carbonate is ${\text{Al}}_2{\left({\text{CO}}_3\right)}_3$. The atomic mass of aluminum, carbon and oxygen is $\text{26}\text{.98}\text{u}$, $\text{12}\text{.01}\text{u}$ and $\text{16}\text{.00}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}{\text{Al}}_2{\left({\text{CO}}_3\right)}_3=\left(\begin{array}{l}2\times \text{Atomic}\text{mass}\text{of}\text{Al}+\\ 3\times \text{Atomic}\text{mass}\text{of}\text{C}+\text{9}\times \text{Atomic}\text{mass}\text{of}\text{O}\end{array}\right)$

Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}{\text{Al}}_2{\left({\text{CO}}_3\right)}_3& =& \left(\begin{array}{l}2\times \text{Atomic}\text{mass}\text{of}\text{Al}+\\ 3\times \text{Atomic}\text{mass}\text{of}\text{C}+\text{9}\times \text{Atomic}\text{mass}\text{of}\text{O}\end{array}\right)\\ & =& \left(2\times \text{26}\text{.98}\text{u}\right)+\left(3\times \text{12}\text{.01}\text{u}\right)+\left(\text{9}\times \text{16}\text{.00}\text{u}\right)\\ & =& \text{53}\text{.96}\text{u}+\text{36}\text{.03}\text{u}+\text{144}\text{u}\\ & =& \text{233}\text{.99}\text{u}\end{array}$

Thus, the formula mass of aluminum carbonate is $\text{233}\text{.99}\text{u}$.

Conclusion

The formula mass of aluminum carbonate is $\text{233}\text{.99}\text{u}$.

Interpretation Introduction

(c)

Interpretation:

The formula mass of ammonium sulfate is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass of ammonium sulfate is $\text{132}\text{.15}\text{u}$.

Explanation of Solution

The chemical formula for ammonium sulfate is ${\left({\text{NH}}_4\right)}_2{\text{SO}}_4$. The atomic mass of nitrogen, hydrogen, sulfur and oxygen is $\text{14}\text{.01}\text{u}$, $\text{1}\text{.008}\text{u}$, $32.07\text{u}$ and $\text{16}\text{.00}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}{\left({\text{NH}}_4\right)}_2{\text{SO}}_4=\left(\begin{array}{l}2\times \text{Atomic}\text{mass}\text{of}\text{N}+8\times \text{Atomic}\text{mass}\text{of}\text{H}\\ +\text{Atomic}\text{mass}\text{of}\text{S}+\text{4}\times \text{Atomic}\text{mass}\text{of}\text{O}\end{array}\right)$

Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}{\left({\text{NH}}_4\right)}_2{\text{SO}}_4& =& \left(\begin{array}{l}2\times \text{Atomic}\text{mass}\text{of}\text{N}+8\times \text{Atomic}\text{mass}\text{of}\text{H}\\ +\text{Atomic}\text{mass}\text{of}\text{S}+\text{4}\times \text{Atomic}\text{mass}\text{of}\text{O}\end{array}\right)\\ & =& \left(2\times \text{14}\text{.01}\text{u}\right)+\left(8\times \text{1}\text{.008}\text{u}\right)+32.07\text{u}+\left(4\times \text{16}\text{.00}\text{u}\right)\\ & =& \text{28}\text{.02}\text{u}+\text{8}\text{.064}\text{u}+32.07\text{u}+\text{64}\text{u}\\ & =& \text{132}\text{.15}\text{u}\end{array}$

Thus, the formula mass of ammonium sulfate is $\text{132}\text{.15}\text{u}$.

Conclusion

The formula mass of ammonium sulfate is $\text{132}\text{.15}\text{u}$.

Interpretation Introduction

(d)

Interpretation:

The formula mass or molecular mass of butane, ${\text{C}}_{\text{4}}{\text{H}}_{\text{10}}$ is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass or molecular mass of butane, ${\text{C}}_{\text{4}}{\text{H}}_{\text{10}}$ is $\text{58}\text{.12}\text{u}$.

Explanation of Solution

The chemical formula for butane is ${\text{C}}_{\text{4}}{\text{H}}_{\text{10}}$. The atomic mass hydrogen and carbon is $\text{1}\text{.008}\text{u}$ and $\text{12}\text{.01}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}{\text{C}}_{\text{4}}{\text{H}}_{\text{10}}=4\times \text{Atomic}\text{mass}\text{of}\text{C}+10\times \text{Atomic}\text{mass}\text{of}\text{H}$

Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}{\text{C}}_{\text{4}}{\text{H}}_{\text{10}}& =& 4\times \text{Atomic}\text{mass}\text{of}\text{C}+10\times \text{Atomic}\text{mass}\text{of}\text{H}\\ & =& \left(4\times \text{12}\text{.01}\text{u}\right)+\left(10\times \text{1}\text{.008}\text{u}\right)\\ & =& 4\text{8}\text{.04}\text{u}+10.\text{08}\text{u}\\ & =& \text{58}\text{.12}\text{u}\end{array}$

Thus, the formula mass or molecular mass of butane is $\text{58}\text{.12}\text{u}$.

Conclusion

The formula mass or molecular mass of butane, ${\text{C}}_{\text{4}}{\text{H}}_{\text{10}}$ is $\text{58}\text{.12}\text{u}$.

Interpretation Introduction

(e)

Interpretation:

The formula mass of silver nitrate is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass of silver nitrate is $\text{169}\text{.9}\text{u}$.

Explanation of Solution

The chemical formula for silver nitrate is ${\text{AgNO}}_{\text{3}}$. The atomic mass of nitrogen, silver and oxygen is $\text{14}\text{.01}\text{u}$, $\text{107}\text{.9}\text{u}$ and $\text{16}\text{.00}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}{\text{AgNO}}_{\text{3}}=\text{Atomic}\text{mass}\text{of}\text{Ag}+\text{Atomic}\text{mass}\text{of}\text{N}+\text{3}\times \text{Atomic}\text{mass}\text{of}\text{O}$ Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}{\text{AgNO}}_{\text{3}}& =& \text{Atomic}\text{mass}\text{of}\text{Ag}+\text{Atomic}\text{mass}\text{of}\text{N}+\text{3}\times \text{Atomic}\text{mass}\text{of}\text{O}\\ & =& \left(\text{107}\text{.9}\text{u}\right)+\left(\text{14}\text{.01}\text{u}\right)+\left(3\times \text{16}\text{.00}\text{u}\right)\\ & =& \text{107}\text{.9}\text{u}+\text{14}\text{.01}\text{u}+48\text{u}\\ & =& \text{169}\text{.9}\text{u}\end{array}$

Thus, the formula mass of silver nitrate is $\text{169}\text{.9}\text{u}$.

Conclusion

The formula mass of silver nitrate is $\text{169}\text{.9}\text{u}$.

Interpretation Introduction

(f)

Interpretation:

The formula mass of manganese $\left(\text{IV}\right)$ oxide is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass of manganese $\left(\text{IV}\right)$ oxide is $\text{86}\text{.94}\text{u}$.

Explanation of Solution

The chemical formula for manganese $\left(\text{IV}\right)$ oxide is ${\text{MnO}}_2$. The atomic mass of manganese and oxygen is $\text{54}\text{.94}\text{u}$ and $\text{16}\text{.00}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}{\text{MnO}}_2=\text{Atomic}\text{mass}\text{of}\text{Mn}+\text{2}\times \text{Atomic}\text{mass}\text{of}\text{O}$

Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}{\text{MnO}}_2& =& \text{Atomic}\text{mass}\text{of}\text{Mn}+\text{2}\times \text{Atomic}\text{mass}\text{of}\text{O}\\ & =& \text{54}\text{.94}\text{u}+\left(2\times \text{16}\text{.00}\text{u}\right)\\ & =& \text{54}\text{.94}\text{u}+32\text{u}\\ & =& \text{86}\text{.94}\text{u}\end{array}$

Thus, the formula mass of manganese $\left(\text{IV}\right)$ oxide is $\text{86}\text{.94}\text{u}$.

Conclusion

The formula mass of manganese $\left(\text{IV}\right)$ oxide is $\text{86}\text{.94}\text{u}$.

Interpretation Introduction

(g)

Interpretation:

The formula mass of zinc phosphate is to be calculated.

Concept introduction:

The atomic mass of an atom is defined as the average of the total masses of the atoms in an element. Similarly, in case of molecules, the average mass of molecules is known as molecular mass. Formula mass is the mass of the atoms present in a molecular formula.

Answer to Problem 7E

The formula mass of zinc phosphate is $\text{386}\text{.17}\text{u}$.

Explanation of Solution

The chemical formula for zinc phosphate is ${\text{Zn}}_3{\left({\text{PO}}_4\right)}_2$. The atomic mass of zinc, phosphorus and oxygen is $\text{65}\text{.41}\text{u}$, $\text{30}\text{.97}\text{u}$ and $\text{16}\text{.00}\text{u}$ respectively. The formula mass can be calculated using the formula given below as,

$\text{Formula}\text{mass}\text{of}{\text{Zn}}_3{\left({\text{PO}}_4\right)}_2=\left(\begin{array}{l}3\times \text{Atomic}\text{mass}\text{of}\text{Zn}+2\times \text{Atomic}\text{mass}\text{of}\text{P}+\\ \text{8}\times \text{Atomic}\text{mass}\text{of}\text{O}\end{array}\right)$

Substitute the values in the above equation as,

$\begin{array}{rll}\text{Formula}\text{mass}\text{of}{\text{Zn}}_3{\left({\text{PO}}_4\right)}_2& =& \left(\begin{array}{c}3\times \text{Atomic}\text{mass}\text{of}\text{Zn}+2\times \text{Atomic}\text{mass}\text{of}\text{P}+\\ \text{8}\times \text{Atomic}\text{mass}\text{of}\text{O}\end{array}\right)\\ & =& \left(3\times \text{65}\text{.41}\text{u}\right)+\left(2\times \text{30}\text{.97}\text{u}\right)+\left(8\times \text{16}\text{.00}\text{u}\right)\\ & =& \text{196}\text{.23}\text{u}+61.94\text{u}+128\text{u}\\ & =& \text{386}\text{.17}\text{u}\end{array}$

Thus, the formula mass of zinc phosphate is $\text{386}\text{.17}\text{u}$.

Conclusion

The formula mass of zinc phosphate is $\text{386}\text{.17}\text{u}$.