Chapter 6, Problem 25A

(a)

Interpretation Introduction

Interpretation:

The number of molecules present in the samples needs to be predicted.

Concept Introduction:

Mole is the amount of the substance that contains the same number of particles or atoms or molecules. Molar mass is defined as an average mass of atoms present in the chemical formula. It is the sum of the atomic masses of all the atoms present in the chemical formula of any compound.

Answer to Problem 25A

Number of molecules of CO in 6.37 mol = 3.836 ×10²² molecules

Explanation of Solution

Number of molecules in 6.37 mol of carbon monoxide

Number of carbon monoxide molecules = Number of moles × Avogadro number

                                 = 6.37 mol × (6.022140857 × 10²³ molecules / mol)

                                    = 38.361 × 10²³ molecules

                                    = 3.836 ×10²² molecules

(b)

Interpretation Introduction

Interpretation:

The number of molecules present in the samples needs to be predicted.

Concept Introduction:

Mole is the amount of the substance that contains the same number of particles or atoms or molecules. Molar mass is defined as an average mass of atoms present in the chemical formula. It is the sum of the atomic masses of all the atoms present in the chemical formula of any compound.

Answer to Problem 25A

Number of molecules of CO in 6.37 g = 1.37 × 10²³ molecules

Explanation of Solution

Number of molecules in 6.37 g carbon monoxide

 Molecular formula = CO            

Molecular mass = 28.01 g/ mol  

Given,

Mass of CO = 6.37g

The calculation of moles is shown below:

  $\begin{array}{l}\text{Number of moles of CO = }\frac{\text{Mass of CO }}{\text{Molecular mass of CO}}\hfill \\ \text{ = }\frac{\text{6}\text{.37 g}}{\text{28}\text{.01 g/ mol}}\hfill \\ \text{ = 0}\text{.227418779 moles}\hfill \end{array}$

Number of CO molecules = Number of moles × Avogadro number

                                    = 0.227418779 mol × (6.022140857 × 10²³ molecules / mol)

                                    = 1.37 ×10²³ molecules

(c)

Interpretation Introduction

Interpretation:

The number of molecules present in the samples needs to be predicted.

Concept Introduction:

Mole is the amount of the substance that contains the same number of particles or atoms or molecules. Molar mass is defined as an average mass of atoms present in the chemical formula. It is the sum of the atomic masses of all the atoms present in the chemical formula of any compound.

Answer to Problem 25A

Number of molecules of H₂O in 2.62 ×10-6 g = 8.76× 10¹⁶ molecules

Explanation of Solution

Number of molecules in 2.62×10-6 g water

Molecular formula = H₂O           

 Molecular mass = 18g/ mol  

Given,

Mass of H₂O = 2.62×10-6 g

The calculation of moles is shown below:

  $\begin{array}{l}{\text{Number of moles of H}}_{\text{2}}\text{O = }\frac{{\text{Mass of H}}_{\text{2}}\text{O }}{{\text{Molecular mass of H}}_{\text{2}}\text{O}}\hfill \\ \text{ = }\frac{\text{2}\text{.62}\text{×}{\text{10}}^{\text{-6}}\text{ g}}{\text{18 g/ mol}}\hfill \\ \text{ = 1}\text{.4555}\text{×}{\text{10}}^{\text{-7}}\text{ moles}\hfill \end{array}$

Number of H₂O molecules = Number of moles × Avogadro number

                                    = 1.4555 ×10-7 mol × (6.022140857 × 10²³ molecules / mol)

                                    = 8.76 ×10¹⁶ molecules

(d)

Interpretation Introduction

Interpretation:

The number of molecules present in the samples needs to be predicted.

Concept Introduction:

Mole is the amount of the substance that contains the same number of particles or atoms or molecules. Molar mass is defined as an average mass of atoms present in the chemical formula. It is the sum of the atomic masses of all the atoms present in the chemical formula of any compound.

Answer to Problem 25A

Number of molecules of H₂O in 2.62× 10-6 mol = 1.58 ×10¹⁸ molecules

Explanation of Solution

 Number of molecules in 2.62 × 10-6 mol of water

Number of water molecules = Number of moles × Avogadro number

                                    = 2.62 × 10-6 mol × (6.022140857 × 10²³ molecules / mol)

                                    = 15.78 × 10¹⁷ molecules

                                    = 1.58 ×10¹⁸ molecules

(e)

Interpretation Introduction

Interpretation:

The number of molecules present in the samples needs to be predicted.

Concept Introduction:

Mole is the amount of the substance that contains the same number of particles or atoms or molecules. Molar mass is defined as an average mass of atoms present in the chemical formula. It is the sum of the atomic masses of all the atoms present in the chemical formula of any compound.

Answer to Problem 25A

Number of molecules of C₆H₆ in 5.23 g = 4.029× 10²² molecules

Explanation of Solution

Number of molecules in 5.23 g benzene

Molecular formula = C₆H₆            

Molecular mass = 78.11 g/ mol  

Given,

Mass of C₆H₆= 5.23 g

The calculation of moles is shown below:

  $\begin{array}{l}{\text{Number of moles of C}}_6{\text{H}}_6\text{ = }\frac{{\text{Mass of C}}_6{\text{H}}_6}{{\text{Molecular mass of C}}_6{\text{H}}_6}\hfill \\ \text{ = }\frac{\text{5}\text{.23 g}}{\text{78}\text{.11 g/ mol}}\hfill \\ \text{ =}\text{0}\text{.0669 moles}\hfill \end{array}$

Number of C6H6 molecules = Number of moles × Avogadro number

                                    = 0.0669 mol × (6.022140857 × 10²³ molecules / mol)

                                    = 4.029 ×10²² molecules