Chapter 6, Problem 17A

(a)

Interpretation Introduction

Interpretation: The number of Cobalt atoms in 0.00103 g needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

  $\text{1}{\text{.05 ×10}}^{\text{19}}\text{ atoms}$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Mass of Co given = 0.00103 g

1 mole = 6.022 x 10²³atoms

Calculate number of atoms:

  $\text{0}\text{.00103 g ×}\frac{\text{1 mole}}{\text{58}\text{.93 g}}\text{ ×}\frac{\text{6}{\text{.022×10}}^{\text{23}}\text{atoms}}{\text{1 mole}}\text{ =1}{\text{.05 ×10}}^{\text{19}}\text{ atoms}$

(b)

Interpretation Introduction

Interpretation: The number of Cobalt atoms in 0.00103 mole needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

  $\text{6}{\text{.20 ×10}}^{\text{20}}\text{ atoms}$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Moles of Co given = 0.00103 moles

1 mole = 6.022 x 10²³atoms

Calculate number of atoms:

  $\text{0}\text{.00103 moles ×}\frac{\text{6}{\text{.022×10}}^{\text{23}}\text{atoms}}{\text{1 mole}}\text{ =6}{\text{.20 ×10}}^{\text{20}}\text{ atoms}$

(c)

Interpretation Introduction

Interpretation: The number of moles of Cobalt in 2.75 g needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

  $0.047moles$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Mass of Co given = 2.75 g

1 mole = 6.022 x 10²³atoms

Calculate number of moles:

  $2.75g\times \frac{1mole}{58.93g}=0.047moles$

(d)

Interpretation Introduction

Interpretation: The number of moles of Cobalt in 5.99 x 10²¹ cobalt atoms needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

  $\text{9}{\text{.94×10}}^{\text{-3}}\text{moles}$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Number of atoms of Co given = 5.99 x 10²¹

1 mole = 6.022 x 10²³atoms

Calculate number of moles:

  $\text{5}{\text{.99× 10}}^{\text{21}}\text{ ×}\frac{\text{1 mole }}{\text{6}{\text{.022×10}}^{\text{23}}\text{atoms}}\text{ = 9}{\text{.94×10}}^{\text{-3}}\text{moles}$

(e)

Interpretation Introduction

Interpretation: The mass of 4.23 moles of Cobalt needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

Mass = $\text{ 249 g}$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Moles of Co given = 4.23 moles

1 mole = 6.022 x 10²³atoms

Calculate mass:

  $\text{4}\text{.23 moles ×}\frac{\text{58}\text{.93 g }}{\text{1 mole }}\text{ = 249 g}$

(f)

Interpretation Introduction

Interpretation: The number of Co atoms in 4.23 moles of Cobalt needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

  $\text{25}{\text{.5× 10}}^{\text{23}}\text{atoms}$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Moles of Co given = 4.23 moles

1 mole = 6.022 x 10²³atoms

Calculate number of atoms:

  $\text{4}\text{.23 moles ×}\frac{\text{6}{\text{.022× 10}}^{\text{23}}\text{atoms }}{\text{1 mole }}\text{ = 25}{\text{.5× 10}}^{\text{23}}\text{atoms}$

(g)

Interpretation Introduction

Interpretation: The number of Co atoms in 4.23 g of Cobalt needs to be determined.

Concept Introduction: The molecular mass of a compound is the sum of the atomic mass of all the atoms present in the given chemical compound. Mole concept is used to calculate the moles, mass, number of atoms and moles of a compound. The relation between these values can be shown as:

  $\begin{array}{l}\text{Moles = }\frac{\text{mass}}{\text{molar mass}}\\ {\text{1 mole = N}}_{\text{a}}\text{ atoms}\\ {\text{N}}_{\text{a}}\text{ = 6}\text{.022 }\times {\text{ 10}}^{\text{23}}\end{array}$

Answer to Problem 17A

  $\text{4}{\text{.32× 10}}^{\text{22}}\text{atoms}$

Explanation of Solution

Molar mass of Co = 58.93 g/mol

Mass of Co given = 4.23 g

1 mole = 6.022 x 10²³atoms

Calculate number of atoms:

  $\text{4}\text{.23 g ×}\frac{\text{1 mole}}{\text{58}\text{.93g}}\times \frac{\text{6}{\text{.022× 10}}^{\text{23}}\text{atoms }}{\text{1 mole }}\text{ = 4}{\text{.32× 10}}^{\text{22}}\text{atoms}$