When air pollution is high, ozone \(\left(\mathrm{O}_{3}\right)\) contents can reach \(0.60 \mathrm{ppm}\) (i.e., \(0.60\) mol ozone per million mol air). How many molecules of ozone are present per liter of polluted air if the barometric pressure is \(755 \mathrm{~mm} \mathrm{Hg}\) and the temperature is \(79^{\circ} \mathrm{F} ?\)

The Ideal Gas Law is a fundamental principle in chemistry and physics that describes the behavior of gases under various conditions. It is expressed by the equation
\[PV = nRT\]
where P represents the pressure of the gas, V is the volume it occupies, n is the amount in moles, R is the ideal gas constant (0.0821 L.atm/K.mol), and T is the temperature in Kelvin (K). This law allows us to calculate any one of these variables if the others are known.
When solving problems related to the concentration of substances in the air, such as the given exercise, the Ideal Gas Law is indispensable. It enables us to determine the volume of air—or any gas—in a given space, which is essential for calculating concentrations.

Application in Pollution Measurement

In environmental studies, the Ideal Gas Law helps assess the amount of pollutants in the air by establishing the relationship between gas volumes and mole quantities. By figuring out the number of moles of a gas in a specific volume, we can proceed to find the concentration of the pollutants, provided that their volumetric proportions are known.

Avogadro's number is a constant that is central to chemistry and defines the number of constituent particles, usually atoms or molecules, that are contained in one mole of a substance. Avogadro's number is approximately
\(6.022 \times 10^{23}\)
particles per mole.
This number makes a bridge between the macroscopic world we can measure and the microscopic world of molecules and atoms. So, when we talk about a 'mole' of any substance, we are referring to a quantity that contains as many elementary entities as there are atoms in exactly 12 grams of carbon-12, which is Avogadro's number.

Connecting Moles to Molecules

Using Avogadro's number, we can convert moles of a gas into individual molecules, which is exactly what was done in the solution to determine the number of ozone molecules per liter of air. This conversion is essential in environmental chemistry, where it's often necessary to discuss quantities at the molecular level to understand the impact of pollutants on the environment and human health.

Environmental chemistry is the branch of science that focuses on the chemical phenomena occurring in the environment. It involves the study of the sources, reactions, transport, effects, and fates of chemical species in the water, soil, and air environments, as well as the effect of human activity upon these.
Understanding environmental chemistry is essential when addressing issues like air pollution. Pollutants like ozone (\(\text{O}_3\)) can have significant health impacts, and their concentration in the atmosphere needs to be carefully monitored. The concentration of ozone and other pollutants in the air is often expressed in parts per million (ppm), as seen in the textbook example.

Role in Pollution Tracking

Environmental chemistry provides the tools and concepts needed to quantify and analyze pollutants. By applying principles such as the Ideal Gas Law and using Avogadro's number, we can calculate the exact amount of a given substance in a particular volume of air, enabling us to better understand and mitigate potential environmental risks and ensure regulatory compliance.