Chapter 6, Problem 64A

Interpretation Introduction

Interpretation: The sample with the greatest percent by mass of nitrogen needs to be determined.

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:

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

Answer to Problem 64A

Correct answer: (d)

Mass percentage of N = 39.0 %

Explanation of Solution

Reason for correct option:

Molar mass of $\text{Ca}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}$ = 164 g/mol

Substitute the values to calculate mass percentage of N:

  $\begin{array}{l}\text{Mass percentage = }\frac{\text{Number of N × mass of N}}{\text{molar mass of compound}}\times 100\\ \text{Mass percentage = }\frac{\text{6 × 14}\text{.0 g/mol}}{\text{164 g/mol}}\times 100=39.0\%\end{array}$

All the samples have same molecular formula therefore the mass percentage of N will be same.

Conclusion

Reasons for incorrect options:

The mass percentage of an element in a chemical compound remains same with change in moles as it depends on chemical formula.