Question

5. (12 pts total) Answer the following questions using the information below: Reaction (1): C1+03 → CIO + O2 Reaction (2): 0+ CIO → C1 + 02 Reaction (3): Cl + CH4 → HCl + CH3 Reaction (4): 0+03 → 02 +02 kı = 9.1x10-¹2 cm³ molecule-¹ s-¹ k₂= 4.1x10-¹1 cm³ molecule-¹ s-¹ k3= 2.2x10-¹4 cm³ molecule-¹ s-¹ k4 = 8.5x10-¹6 cm³ molecule-¹ s-¹ Mixing ratios (i.e., Xz, where z is Cl, O3, O, CIO or CH4) by volume at 30 km altitude: Cl=1.7x10-¹3 (i.c., 0.17 ppt or parts-per-trillion), O3-8.3×10-6, 0-8.9×10-¹¹, CIO=1.9×10-10, CH4=6.7x10-7. The total pressure at 30 km is 1.13% of its value at the ground, and the temperature is 224 K. a. (2 pts) Re-arrange the ideal gas law to express concentration in terms of pressure and temperature. Use this expression to calculate the concentration of air at 30 km altitude, in units of the number of air molecules per cubic centimeter of air. (The answer is 3.7×10¹7 molecules/cm³) b. (2 pts) Calculate the concentrations of Cl, O3, O, CIO and CH4. c. (2 pts) Reaction (2) is the rate-determining step of the chlorine catalytic cycle. At what rate is odd oxygen destroyed by chlorine radicals? (Hint: to answer this, remember that "odd oxygen destruction" includes loss of both O and O3) d. (3 pts) What is the lifetime of odd oxygen from loss in the fourth reaction of the Chapman scheme (i.e., Reaction 4, above)? What is the lifetime via chlorine catalysis (use your answer from (c))? Based on your calculation, is chlorine catalysis important for ozone loss relative to the rate of loss via Chapman chemistry? e. (3 pts) Assuming that the only important chemistry involving chlorine-containing radicals is that shown above, calculate how many odd oxygen molecules are destroyed by a single Cl atom before that chlorine atom is converted to HCl. (Hint: To do this, try comparing the lifetime for loss of Cl atoms via reaction with ozone to that for loss via reaction with CH4.)

Get Instant Homework HelpOn Your Mobile

Get Instant Homework HelpOn Your Mobile

Get Instant Homework HelpOn Your Mobile