Key constants and parameters: R=0.08206 Latmmol-1K-1: R=8.314 Pam3mol-1K-1: 0C = 273 K: NAv=6.02x1023: Mass atmosphere = 5.1x1021 g: Average Mol. Mass atmosphere = 29.0 gmol-1: 1 Gt=Gigatonne = 1x1015 g: 1 Mt=Megatonne = 1 Tg=Teragram = 1x1012 g: 1 m3 = 1000 L = 1x106 cm3: 1 L water = 1 kg.

1. At an altitude of 22 km, the concentration of O3 in the stratosphere is 2.92 ppm (50 C and 0.0500 atm).

a) Calculate the density of O3 in molec.cm-3 units at 22 km altitude.

b) Calculate the concentration of O3 in gm-3 at 22 km altitude.

2. At an altitude of 33 km, the concentration of O3 in the stratosphere is 6.76 ppm (25 C and 0.0100 atm).

a) Calculate the density of O3 in molec.cm-3 units at 33 km altitude.

b) Calculate the concentration of O3 in gm-3 at 33 km altitude.

3. Compare the answers for question 1 with those from question 2. Explain in a few sentences why the concentrations in molec.cm-3 units follow a different trend than the ppm concentrations (i.e. one is larger at the higher altitude, the other is larger at the lower altitude).