Chapter 10.3, Problem 33SP

Interpretation Introduction

Interpretation: The percent composition of the compound formed by combining 9.03 g $\text{Mg}$ with 3.48 g $\text{N}$ should be calculated.

Concept Introduction: The percent composition represents the relative amount of the elements in a compound. It is represented as the percent by mass of each element in the compound.

Answer to Problem 33SP

The mass percent composition of $\text{Mg}$ and $\text{N}$ in the compound is $72.18\%$ and $27.82\%$ respectively.

Explanation of Solution

The percent by mass of each element in the compound represents the percent composition as:

  $\text{percent by mass of an element = }\frac{\text{mass of an element}}{\text{mass of the compound}}\times 100\%$   ...... (1)

The mass of the compound formed by combining 9.03 g $\text{Mg}$ with 3.48 g $\text{N}$ is:

  $\text{mass of compound = 9}\text{.03 g + 3}\text{.48 g = 12}\text{.51 g}$

Now, determining the percent composition of $\text{Mg}$ using relation (1):

  $\begin{array}{l}\text{\%Mg = }\frac{\text{mass of Mg}}{\text{mass of the compound}}\times 100\%\\ \text{\%Mg}=\frac{\text{9}\text{.03 g}}{\text{12}\text{.51 g}}\times 100\%\\ \text{\%Mg = }72.18\%\end{array}$

Now, determining the percent composition of $\text{N}$ using relation (1):

  $\begin{array}{l}\text{\%N = }\frac{\text{mass of N}}{\text{mass of the compound}}\times 100\%\\ \text{\%N = }\frac{\text{3}\text{.48 g}}{\text{12}\text{.51 g}}\times 100\%\\ \text{\%N = }27.82\%\end{array}$

The obtained percent of the elements adds up to:

  $\text{72}\text{.81 \% + 27}\text{.82 \% = 100\%}$