Q1(g). Rate constant in dm³ mol⁻¹ s⁻¹

Answer in brief

k = 4.8 × 10⁶ dm³ mol⁻¹ s⁻¹ (4.8 × 10³ m³ mol⁻¹ s⁻¹).

Key points

• Unit (concentration)⁻¹ time⁻¹ ⇒ second order: rate = k[O][O₃].
• Per molecule → per mole: k = 8.0 × 10⁻¹⁵ × 6.022 × 10²³ = 4.82 × 10⁹ cm³ mol⁻¹ s⁻¹.
• 1 cm³ = 10⁻³ dm³: k = 4.82 × 10⁹ × 10⁻³ = 4.8 × 10⁶ dm³ mol⁻¹ s⁻¹.
• This is the odd-oxygen loss step of the Chapman cycle in the stratosphere.