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Constructing a Model of ppbv of Surface Ozone

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## Constructing a Model of ppbv of Surface Ozone

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**Constructing a Model of ppbv of Surface Ozone**GLOBE Ozone Protocol Learning Activity**Look at the NumbersComposition of Earth’s Dry**Atmosphere(1976 Standard Atmosphere*)**Expressing concentration of a gas**parts per billion volume number density**Let’s look at volume of ozone in this classroom**Example: Ozone (trace gas) is probably ~ 20 ppbv in this room. This means that ~ 20 billionths of the volume of gas in this room is ozone. Suppose this room is 6 m wide by 9 m long by 3 m high V = 6 m x 9 m x 3 m V = 162 m3 = 162,000,000 cm3 = 162 x 106 cm3 So what is the volume of ozone in this room? (20 billionths)(162 million cm3) = (20 x 10-9)(162 x 106 cm3) = 3.240 cm3 ~ 3 cm3 ozone in this room**How many molecules of gas in 1 cm3?**From ideal gas law, in 1 cm3 of air at 25°C and 1 atm, there are 2.5 x 1019molecules “25 billion billion” molecules in 1 cm3**Let’s look at number density for ozone**Example: Ozone (trace gas) is probably ~ 20 ppbv in this room What is number density of ozone(2.5 x 1019 molecules/cm3)(20 x 10-9) =50 x 1010 molecules ozone/cm3 =500 x 109 molecules ozone/cm3 or 500 billion molecules ozone/cm3