Chapter 6, Problem 9STP

Interpretation Introduction

Interpretation: The species containing 46.7 % mass percentage of nitrogen needs to be determined from the given options.

Concept Introduction: Mass percentage is the way to calculate the percentage of each element in the given molecular compounds. The mathematical expression of mass percentage can be shown as:

  $\text{Mass percentage = }\frac{\text{Number of element × mass of N}}{\text{molar mass of compound}}\times 100$

Answer to Problem 9STP

Correct answer: Option (C)

Explanation of Solution

Reason for correct option:

Molar mass of N = 14.00 g/mol

Molar mass of NO = 30.0 g/mol

Calculate the mass percentage of N in each compound:

  $\text{Mass percentage of N in NO = }\frac{\text{1 × 14}\text{.00 g/mol}}{\text{30}\text{.0 g/mol}}\times 100=46.7\%$

Thus NO has 46.7% N by mass.

Conclusion

Reasons for incorrect options:

Molar mass of N = 14.00 g/mol

Molar mass of N₂O₅ = 108 g/mol

Molar mass of NO₂ = 46.0 g/mol

Molar mass of N₂O = 44.0 g/mol

Calculate the mass percentage of N in each compound:

  $\begin{array}{l}{\text{Mass percentage of N in N}}_{\text{2}}{\text{O}}_{\text{5}}\text{ = }\frac{\text{2 × 14}\text{.00 g/mol}}{\text{108 g/mol}}\times 100=25.9\%\\ {\text{Mass percentage of N in NO}}_{\text{2}}\text{= }\frac{\text{1 × 14}\text{.00 g/mol}}{\text{46}\text{.0 g/mol}}\times 100=30.4\%\\ {\text{Mass percentage of N in N}}_{\text{2}}\text{O = }\frac{\text{2 × 14}\text{.00 g/mol}}{\text{44 g/mol}}\times 100=63.6\%\end{array}$