Chapter 3, Problem 3.16P

(a)

Interpretation Introduction

Interpretation:

The mass of $6.44\times {10}^{-2}\text{ mol}$ of ${\text{MnSO}}_4$ in grams is to be calculated.

Concept introduction:

Molar mass is defined as the mass of $1\text{ mol}$ of a chemical substance in grams. The molar mass of a compound is calculated by the addition of the molar mass of each element multiplied by its number of atoms present in the chemical formula.

Molar mass is used to convert the mass of a substance to moles. The expression to calculate the mass of a chemical substance in grams is as follows:

$\text{Mass }\left(\text{g}\right)=\left(\text{amount}\left(\text{mol}\right)\right)\left(\frac{\text{no}\text{. of grams}}{1\text{ mol}}\right)$

(b)

Interpretation Introduction

Interpretation:

The amount of $15.8\text{ kg}$ of $\text{Fe}{\left({\text{ClO}}_4\right)}_3$ in moles is to be calculated.

Concept introduction:

Molar mass is defined as the mass of $1\text{ mol}$ of a chemical substance in grams. The molar mass of a compound is calculated by the addition of the molar mass of each element multiplied by its number of atoms present in the chemical formula.

Molar mass is used to calculate the mass of a chemical substance in grams. The expression to calculate the mass of a chemical substance in grams is as follows:

$\text{Amount}\left(\text{mol}\right)=\left(\text{Mass }\left(\text{g}\right)\right)\left(\frac{1\text{ mol}}{\text{no}\text{. of grams}}\right)$

(c)

Interpretation Introduction

Interpretation:

The number of $\text{N}$ atoms in $92.6\text{ mg}$ of ${\text{NH}}_4{\text{NO}}_2$ is to be calculated.

Concept introduction:

One mole is defined as the amount of substance that contains the same number of entities such as molecules, ions, atoms as the number of atoms in $12\text{ g}$ of $\text{C-12}$. This number is called Avogadro’s number. The value of Avogadro’s number is $\text{6}\text{.022}\times {\text{10}}^{23}\left(\text{entitites/mol}\right)$.

Molar mass is defined as the mass of $1\text{ mol}$ of a chemical substance in grams. The molar mass of a compound is calculated by the addition of the molar mass of each element multiplied by its number of atoms present in the chemical formula.

The molecular formula of a compound tells the number of atoms/ions of each element present in the compound.

Following are the steps to calculate the number of atoms in a compound.

Step 1: Convert the mass of the compound to moles by using the molar mass of that compound as follows:

$\text{Amount}\left(\text{mol}\right)=\left(\text{Given mass}\left(\text{g}\right)\right)\left(\frac{1\text{ mol}}{\text{No}\text{. of grams}}\right)$

Step 2: Determine the number of moles of atoms of an element from the molecular formula of the compound. The formula to calculate the moles of atoms is as follows:

$\text{Amount of atoms}\left(\text{mol}\right)=\left(\begin{array}{l}\text{amount of}\\ \text{compound}\\ \left(\text{mol}\right)\end{array}\right)\left(\frac{\begin{array}{l}\text{moles of atoms in}\\ \text{molecular formula}\end{array}}{1\text{ mol compound}}\right)$

Step 3: Determine the number of atoms by multiplying the moles of atoms with the Avogadro’s number. The expression to calculate the number of atoms of an element is as follows:

$\text{Number of atoms}=\left(\text{Amount }\left(\text{mol}\right)\right)\left(\frac{6.022\times {10}^{23}\text{ atoms}}{1\text{ mol}}\right)$