Chapter 13, Problem 13.1P

What is the mass of the molecular ion formed from compounds having each molecular formula: (a) ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{O}$;(b) ${\text{C}}_{\text{10}}{\text{H}}_{\text{20}}$;(c) ${\text{C}}_{\text{8}}{\text{H}}_{\text{8}}{\text{O}}_{\text{2}}$;(d) methamphetamine $\left({\text{C}}_{\text{10}}{\text{H}}_{\text{15}}\text{N}\right)$?

Interpretation Introduction

(a)

Interpretation: The mass of the molecule ion formed by given compound is to be determined.

Concept introduction: Molecular mass is the sum of the atomic weights of each constituent element multiplied by the number of atoms of that element.

Answer to Problem 13.1P

The mass of the molecule ion formed by ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{O}$ is $58$.

Explanation of Solution

The molecular weight of compound is equal to the mass of the molecular ion. The molecular weight and mass of the given molecular ion is shown below.

$\begin{array}{rll}{\text{Molecular mass of C}}_{\text{3}}{\text{H}}_{\text{6}}\text{O}& =& \left(3\times \text{Mass of C atom + 6}\times \text{Mass of H atom + Mass of O atom}\right)\\ & =& \left(3\times 12+6\times 1+16\right)\\ & =& \left(36+6+16\right)\\ & =& \text{58 g/mol}\end{array}$

Thus, the mass of the molecule ion formed by ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{O}$ is $58$.

Conclusion

The mass of the molecule ion formed by ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{O}$ is $58$.

Interpretation Introduction

(b)

Interpretation: The mass of the molecule ion formed by given compound is to be determined.

Concept introduction: Molecular mass is the sum of the atomic weights of each constituent element multiplied by the number of atoms of that element.

Answer to Problem 13.1P

The mass of the molecule ion formed by ${\text{C}}_{\text{10}}{\text{H}}_{\text{20}}$ is $140$.

Explanation of Solution

The molecular weight of compound is equal to the mass of the molecular ion. The molecular weight and mass of the given molecular ion is shown below.

$\begin{array}{rll}{\text{Molecular mass of C}}_{\text{10}}{\text{H}}_{\text{20}}& =& \left(10\times \text{Mass of C atom + 20}\times \text{Mass of H atom }\right)\\ & =& \left(10\times 12+20\times 1\right)\\ & =& \text{140 g/mol}\end{array}$

Thus, the mass of the molecule ion formed by ${\text{C}}_{\text{10}}{\text{H}}_{\text{20}}$ is $140$.

Conclusion

The mass of the molecule ion formed by ${\text{C}}_{\text{10}}{\text{H}}_{\text{20}}$ is $140$.

Interpretation Introduction

(c)

Interpretation: The mass of the molecule ion formed by given compound is to be determined.

Concept introduction: Molecular mass is the sum of the atomic weights of each constituent element multiplied by the number of atoms of that element.

Answer to Problem 13.1P

The mass of the molecule ion formed by ${\text{C}}_{\text{8}}{\text{H}}_{\text{8}}{\text{O}}_{\text{2}}$ is $136$.

Explanation of Solution

The molecular weight of compound is equal to the mass of the molecular ion. The molecular weight and mass of the given molecular ion is shown below.

$\begin{array}{rll}{\text{Molecular mass of C}}_{\text{8}}{\text{H}}_{\text{8}}{\text{O}}_{\text{2}}& =& \left(8\times \text{Mass of C atom + 8}\times \text{Mass of H atom + 2 }\times \text{Mass of O atom}\right)\\ & =& \left(8\times 12+8\times 1+2\times 16\right)\\ & =& \left(96+8+32\right)\\ & =& \text{136 g/mol}\end{array}$

Thus, the mass of the molecule ion formed by ${\text{C}}_{\text{8}}{\text{H}}_{\text{8}}{\text{O}}_{\text{2}}$ is $136$.

Conclusion

The mass of the molecule ion formed by ${\text{C}}_{\text{8}}{\text{H}}_{\text{8}}{\text{O}}_{\text{2}}$ is $136$.

Interpretation Introduction

(d)

Interpretation: The mass of the molecule ion formed by given compound is to be determined.

Concept introduction: Molecular mass is the sum of the atomic weights of each constituent element multiplied by the number of atoms of that element.

Answer to Problem 13.1P

The mass of the molecule ion formed by ${\text{C}}_{\text{10}}{\text{H}}_{\text{15}}\text{N}$ is $149$.

Explanation of Solution

The molecular weight of compound is equal to the mass of the molecular ion. The molecular weight and mass of the given molecular ion is shown below.

$\begin{array}{rll}{\text{Molecular mass of C}}_{\text{10}}{\text{H}}_{\text{15}}\text{N}& =& \left(10\times \text{Mass of C atom + 15}\times \text{Mass of H atom + Mass of N atom}\right)\\ & =& \left(10\times 12+15\times 1+14\right)\\ & =& \left(120+15+14\right)\\ & =& \text{149 g/mol}\end{array}$

Thus, the mass of the molecule ion formed by ${\text{C}}_{\text{10}}{\text{H}}_{\text{15}}\text{N}$ is $149$.

Conclusion

The mass of the molecule ion formed by ${\text{C}}_{\text{10}}{\text{H}}_{\text{15}}\text{N}$ is $149$.