Chapter 10, Problem 162A

Interpretation Introduction

Interpretation:

The greatest percentage of iron in three naturally occurring iron compounds pyrite, hematite, and siderite should be predicted.

Concept introduction:

The mass percentage of each type of the atoms present in a compound is termed as percentage composition.

Answer to Problem 162A

The mass percent of iron in hematite is greatest.

Explanation of Solution

The expression for mass percentage is given as follows:

$\text{Mass}\text{percentage}=\frac{\text{Mass}\text{of}\text{element}}{\text{Mass}\text{of}\text{compound}}\times 100\%$

Pyrite consist of one atom of iron and two atoms of sulfur thus, the mass percentage of iron in pyrite is calculated as follows:

$\begin{array}{c}\text{Mass}\text{percentage}\text{of}\text{Fe}\text{in pyrite}=\frac{\text{Mass}\text{of}\text{Fe}}{\text{Mass}\text{of}{\text{FeS}}_2}\times 100\%\\ =\frac{55.845}{119.98}\times 100\%\\ \text{Mass}\text{percentage}\text{of}\text{Fe}\text{in pyrite}=46.5\%\end{array}$

Hematite consist of two atoms of iron and three atoms of oxygen thus, the mass percentage of iron in hematite is calculated as follows:

$\begin{array}{c}\text{Mass}\text{percentage}\text{of}\text{Fe}\text{in hematite}=\frac{\text{Mass}\text{of}\text{Fe}}{\text{Mass}\text{of}{\text{Fe}}_2{\text{O}}_3}\times 100\%\\ =\frac{2\times 55.845}{159.63}\times 100\%\\ \text{Mass}\text{percentage}\text{of}\text{Fe}\text{in hematite}=69.97\%\end{array}$

Siderite consist of one atom of iron, carbon and three atoms of oxygen thus, the mass percentage of iron in siderite is calculated as follows:

$\begin{array}{c}\text{Mass}\text{percentage}\text{of}\text{Fe}\text{in siderite}=\frac{\text{Mass}\text{of}\text{Fe}}{\text{Mass}\text{of}{\text{FeCO}}_3}\times 100\%\\ =\frac{55.845}{115.854}\times 100\%\\ \text{Mass}\text{percentage}\text{of}\text{Fe}\text{in siderite}=48.2\%\end{array}$

As the percentage of iron is 46.5%, 69.97%, and 48.2% in pyrite, hematite, and siderite thus, the greatest mass percentage of iron is present in hematite.