Chapter 7, Problem 7.1VP

Interpretation Introduction

To find:

To write the empirical and molecular formulas of the oxides of nitrogen for which two formulas are not the same from the given molecular models in Figure P7.1

Answer to Problem 7.1VP

Solution:

From the given molecular models of oxides of nitrogen, the image (b) has different empirical and molecular formulas as Empirical formula = ${NO}_2$ and Molecular formula =${N_{2}O}_4$.

Explanation of Solution

Empirical formula is the simplest whole number ratio of the atoms of the elements in a compound.

Molecular formula represents the exact number and type of atoms in one molecule of a compound.

Empirical and molecular formulas can be the same or different. For example, consider the two compounds of carbon, carbon dioxide ${CO}_2$ and butane ${C_{4}H}_{10}$.

For carbon dioxide,${CO}_2$ is a simplest whole ratio. We cannot reduce the ratio further without getting fractional values. But, in case of butane, the simplest whole number is ${C_{2}H}_5.$ So, in this case,  the empirical and molecular formulas for carbon dioxide is the same, but for butane the empirical formula is ${C_{2}H}_5$ and molecular formula is ${C_{4}H}_{10}$.

Ball-and-stick or space-filling models like the ones in Figure P7.1 use specific colors for different elements. For example, red is oxygen, blue is nitrogen, black is carbon. Based on this, the molecules in the figure are (a) N₂O₅, (b) N₂O₄, (c) NO, (d) N₂O₃, and (e) NO₂.

Out of these, only one formula, N₂O₄, can be reduced to one smaller whole number, NO₂. SO this is the only oxide for which the empirical and molecular formulas are not the same.

Conclusion:

We compared the ratio of atoms in a molecular formula. For even number of atoms, empirical and molecular formulas are different, but for odd ones, they are the same.