Chapter 6, Problem 55A

Interpretation Introduction

Interpretation: The empirical formula of the two oxides of Cu must be found out.

Concept Introduction:

The empirical formula of a molecule is the smallest unit that is repeated in the molecule.

The molecular formula of a compound is the representation of the molecule with the number of different atoms present in the molecule.

Molecular formula $\text{=empirical formula×n}$ where n is any positive integer like 1, 2, 3 and so on.

Answer to Problem 55A

The empirical formulae of the two oxides of Cu are Cu₂O and CuO.

Explanation of Solution

For the first oxide,

Moles of Cu $=\frac{2.118}{63.5}=\mathrm{0.033.}$

Moles of O $=\frac{0.2666}{16}=\mathrm{0.016.}$

Smallest mole ratio Cu: O will be:

  $\begin{array}{c}R=\frac{0.033}{0.016}:\frac{0.016}{0.016}\\ =2.063:1\\ \approx 2:1.\end{array}$

Thus the compound is Cu₂O.

For the second oxide,

Moles of Cu $=\frac{2.118}{63.5}=\mathrm{0.033.}$

Moles of O $=\frac{0.5332}{16}=\mathrm{0.033.}$

Smallest mole ratio Cu: O will be:

  $\begin{array}{c}R=\frac{0.033}{0.033}:\frac{0.033}{0.033}\\ =1:1\end{array}$

Thus the compound is CuO.

Conclusion

Empirical formulae of the two copper oxides are Cu₂O and CuO.