If the pressure exerted by ozone, o3, in the stratosphere is 3.0×x10−3 atm and the temperature is 250 k , how many ozone molecules are in a liter

Let's assume ideal gas behavior for simplicity. We could use the equation below:

PV=nRT
Solve for n or the number of moles.

n = PV/RT = (3×10⁻³ atm)(1 L)/(0.0821 L·atm/mol·K)(250 K)
n = 1.462×10⁻⁴ moles ozone

For every 1 mole of any substance, Avogadro stipulated that there is an equivalent of 6.022×10²³ molecules. Thus,

# of ozone molecules = 1.462×10⁻⁴ mol *  6.022×10²³ molecules/1 mol
# of ozone molecules = 8.8×10¹⁹

8.7 degrees celsius and 15.6 degrees fahrenheit