Chapter 3.4, Problem 3.15AFP

Interpretation Introduction

Interpretation:

The amount of iron that is formed after the reaction of $1.85\times {10}^{25}$ formula units of iron (III) oxide with aluminum is to be determined. A road map to show the solution is to be included.

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 $\text{6}\text{.022}\times {\text{10}}^{23}\left(\text{entitites/mol}\right)$.

A formula unit is used for the ionic compound to represent their empirical formula. In a balanced chemical equation, the total mass of reactants and products are equal in a balanced chemical equation, thus, it obeyed the law of conservation of mass. Also, the amounts of substances in a balanced chemical reaction are stoichiometrically equivalent to each other.

Following are the steps to determine the amount of a substance when the formula units of other substance present in the chemical reaction are given.

Step 1: Divide the formula unit of the given substance by Avogadro’s number to calculate the moles. The expression to calculate the moles of a chemical substance when the formula units are given is as follows:

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

Step 2: Determine the molar ratio between the substance whose formula unit is given and the substance whose amount is to be calculated from the balanced chemical equation. Multiply the calculated moles in step 1 by the molar ratio to obtain the amount of the substance.