Chapter 3.1, Problem 3.5AFP

(a)

Interpretation Introduction

Interpretation:

The mass of $4.65\times {10}^{22}\text{ molecules}$ of tetraphosphorous decoxide in grams 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.

Following are the steps to calculate the mass of a chemical substance when a number of molecules are given.

Step 1: Determine the amount of substance in moles by using Avogadro’s number. The expression to calculate the moles of a chemical substance is as follows:

$\text{Amount }\left(\text{mol }\right)=\left(\text{Given molecules}\right)\left(\frac{1\text{ mol}}{6.022\times {10}^{23}\text{ molecules}}\right)$

Step 2: Multiply the moles with the molar mass of the chemical substance to obtain the mass of chemical substance in grams. The formula to calculate the mass of a substance in grams is as follows:

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

(b)

Interpretation Introduction

Interpretation:

The number of $\text{P}$ atoms in $4.65\times {10}^{22}\text{ molecules}$ of tetraphosphorous decoxide 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 $\text{6}\text{.022}\times {\text{10}}^{23}\left(\text{entitites/mol}\right)$.

The molecular formula of a compound tells the number of atoms/ions of each element present in the compound. The formula to calculate the number of atoms of an element in when the molecule of a compound is given is as follows:

$\text{Number of atoms}=\left(\begin{array}{l}\text{Molecules of}\\ \text{compound}\end{array}\right)\left(\frac{\begin{array}{l}\text{no}\text{. of atoms of an element in}\\ \text{the molecular formula}\end{array}}{1\text{ molecule of compound}}\right)$