Chapter 6, Problem 42A

Interpretation Introduction

Interpretation: The empirical formula of the compound needs to be determined.

Concept Introduction: The empirical formula is the simplest ratio of atoms of elements present in the compound. It does not tell about the actual number of atoms present in it. Some molecules have empirical formula equal to their molecular formula.

Answer to Problem 42A

CuN₂O₆.

Explanation of Solution

The mass percent of copper, nitrogen and oxygen is 33.88%, 14.94% and 51.18% respectively.

Let the mass of compound be 100 g thus, mass of copper, nitrogen and oxygen will be 33.88 g, 14.94 g and 51.18 g respectively.

From mass, number of moles can be calculated as follows:

  $n=\frac{m}{M}$

The molar mass of copper, nitrogen and oxygen is 63.546 g/mol, 14.0067 g/mol and 15.99 g/mol respectively.

The number of moles of each atom of element can be calculated as follows:

  $\begin{array}{l}{n}_{Cu}=\frac{33.88\text{ g}}{63.546\text{ g/mol}}=0.533\text{ mol}\\ n_N=\frac{14.94\text{ g}}{14.0067\text{ g/mol}}=1.067\text{ mol}\\ n_O=\frac{51.18\text{ g}}{15.99\text{ g/mol}}=3.2\text{ mol}\end{array}$

The ratio of number of moles of Cu, N and O will be 0.533:1.067:3.2 or 1:2:6.

The empirical formula of compound will be CuN₂O₆.

Conclusion

Therefore, the empirical formula of compound will be CuN₂O₆.