Le Bras and Platt (1995) have assessed the ozone depletion caused by CIO and BrO. We...

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Le Bras and Platt (1995) have assessed the ozone depletion caused by CIO and BrO. We will consider the following reactions. Halogen photolysis: Br₂+ hv →→ Br + Br Cl₂+ hv→→ CI+CI Reactions with ozone: Br + 03 → BrO + 0₂ CI+03 → CIO + 0₂ k3 = 7x10¹3 cm³ molee¹ s¹ k4= 1x10-¹¹ cm³ molee¹ s-¹ Regeneration of halogen atoms by reactions with NO: BrO + NO → Br + NO₂ ks =2.5x10 cm³ molec"¹ s¹ CIO + NO → CI+NO₂ k6=2x10 cm³ molec¹ s¹ BrO self-reaction also leads to a catalytic ozone loss cycle: Bro+ BrO → 2Br + 0₂ k7= 3.2x10-¹2 cm³ molec"¹ s²¹ Br + 03 → BrO + 0₂ ks = 7×10-¹2 cm³ molec-¹g-¹ ks = 1.2x10-¹2 cm³ molec-¹ s¹ ksc = 9x10-¹2 cm³ molec"¹ s¹ CIO+ BrO → Cl +Br + 0₂ → BrC1 + 0₂ → Br + OCIO The products BrCl and OCIO easily photolyse: BrCl + hv → Br+ CI OCIO + hy →→0+ CIO TBCI= 53 s Tocio = 6 s (RI) (R2) Sum: 0 + 0→→ 02 +02 + 0₂ (CIO self-reaction leads to the dimer Cl₂O2 and does not directly produce Cl atoms). A mixed cycle can also occur: (R3) (R4) c) Show that the steady-state ratio of [CIO] and [CI] is given by [CIO]/[CI]= (k4[03])/(ko[NO] +(ksa + ks)[BrO]} (R5) (R6) (R7) (R3) (R8a) (R8b) (R8c) (R9) (R10) a) Show that R3 and R7 lead to the overall reaction 203 → 30₂ b) Show that reaction R8c does not lead to net loss of odd oxygen, and that the ozone loss caused by reactions R8a and R8b is: -d[03]/dt = 2(ksa + ksb)[BrO][CIO] Le Bras and Platt (1995) have assessed the ozone depletion caused by CIO and BrO. We will consider the following reactions. Halogen photolysis: Br₂+ hv →→ Br + Br Cl₂+ hv→→ CI+CI Reactions with ozone: Br + 03 → BrO + 0₂ CI+03 → CIO + 0₂ k3 = 7x10¹3 cm³ molee¹ s¹ k4= 1x10-¹¹ cm³ molee¹ s-¹ Regeneration of halogen atoms by reactions with NO: BrO + NO → Br + NO₂ ks =2.5x10 cm³ molec"¹ s¹ CIO + NO → CI+NO₂ k6=2x10 cm³ molec¹ s¹ BrO self-reaction also leads to a catalytic ozone loss cycle: Bro+ BrO → 2Br + 0₂ k7= 3.2x10-¹2 cm³ molec"¹ s²¹ Br + 03 → BrO + 0₂ ks = 7×10-¹2 cm³ molec-¹g-¹ ks = 1.2x10-¹2 cm³ molec-¹ s¹ ksc = 9x10-¹2 cm³ molec"¹ s¹ CIO+ BrO → Cl +Br + 0₂ → BrC1 + 0₂ → Br + OCIO The products BrCl and OCIO easily photolyse: BrCl + hv → Br+ CI OCIO + hy →→0+ CIO TBCI= 53 s Tocio = 6 s (RI) (R2) Sum: 0 + 0→→ 02 +02 + 0₂ (CIO self-reaction leads to the dimer Cl₂O2 and does not directly produce Cl atoms). A mixed cycle can also occur: (R3) (R4) c) Show that the steady-state ratio of [CIO] and [CI] is given by [CIO]/[CI]= (k4[03])/(ko[NO] +(ksa + ks)[BrO]} (R5) (R6) (R7) (R3) (R8a) (R8b) (R8c) (R9) (R10) a) Show that R3 and R7 lead to the overall reaction 203 → 30₂ b) Show that reaction R8c does not lead to net loss of odd oxygen, and that the ozone loss caused by reactions R8a and R8b is: -d[03]/dt = 2(ksa + ksb)[BrO][CIO]

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Step 1 a Overall Reaction from R3 and R 7 The given reactions R3 and R7 are Explanation R3 BrO3 BrO ... View the full answer