Chapter 10, Problem 72A

Interpretation Introduction

Interpretation: To determine the percent composition when 13.3 g $\text{Fe}$ combines completely with 5.7 g $\text{O}$ .

Concept Introduction: The mass percentage of each element in a compound would be indicated by the composition or percent. The combining of two or more components results in a chemical compound.

Answer to Problem 72A

The percent composition of $\text{Fe}$ is $\text{30}\text{\%}$ and oxygen is $\text{70}\text{\%}$ .

Explanation of Solution

The percent composition of Iron can be determined by using the formula:

  $\text{\%}\text{Fe}\text{=}\frac{\text{mass}\text{of}\text{Fe}}{\text{mass}\text{of}{\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}}\text{×100}\text{\%}\mathrm{......}\text{(i)}$

Mass of iron = 13.3 g

Mass of ${\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}$ = $\text{13}\text{.3×2+5}\text{.7×3}\text{=}\text{43}\text{.7}\text{g/mol}$

Mass of oxygen = 5.7 g.

Put the given data in the above equation.

  $\begin{array}{c}\text{\%}\text{Fe}\text{=}\frac{\text{mass}\text{of}\text{Fe}}{\text{mass}\text{of}{\text{Fe}}_{\text{2}}{\text{O}}_{\text{3}}}\text{×100}\text{\%}\\ \text{=}\frac{13.3g}{43.7\text{g/mol}}\text{×100}\text{\%}\\ =30\text{\%}\end{array}$

The % composition of oxygen = $100-30=70\%$