Chapter 3.1, Problem 3.4BFP

Interpretation Introduction

Interpretation:

The number of formula units in $400\text{ lb}$ of ${\text{CaCl}}_2$ per mile of highway 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.

A formula unit is used for the ionic compound to represent their empirical formula. Following is the formula to calculate the number of formula units of an ionic compound from the given mass,

$\text{Number of formula units}=\left(\text{Given mass }\left(\text{g }\right)\right)\left(\frac{\text{1 mol}}{\text{No}\text{. of grams}}\right)\left(\frac{\begin{array}{l}6.022\times {10}^{23}\\ \text{formula units}\end{array}}{1\text{ mol}}\right)$