For the oxidation of sulfur dioxide to sulfur trioxide in the atmosphere

CHEMISTRY · Multi-part · AP · Chemistry · Kinetics · Kinetics

Problem

For the oxidation of sulfur dioxide to sulfur trioxide in the atmosphere, two competing mechanisms have been proposed. Proposed Mechanism I (Homogeneous Gas-Phase): Step 1 SO2  +  O2  ⟶  SO3  +  O\mathrm{SO_2 \; + \; O_2 \; \longrightarrow \; SO_3 \; + \; O} Step 2 O  +  SO2  ⟶  SO3\mathrm{O \; + \; SO_2 \; \longrightarrow \; SO_3} Step 3 O  +  O2  ⟶  O3\mathrm{O \; + \; O_2 \; \longrightarrow \; O_3} Step 4 O3  +  SO2  ⟶  SO3  +  O2\mathrm{O_3 \; + \; SO_2 \; \longrightarrow \; SO_3 \; + \; O_2} Proposed Mechanism II (Catalyzed by Particulate Manganese (II) Ions): Step 1 Mn2+  +  SO2  +  H2O  ⟶  MnSO3  +  2H+\mathrm{Mn^{2+} \; + \; SO_2 \; + \; H_2O \; \longrightarrow \; MnSO_3 \; + \; 2H^+} Step 2 MnSO3  +  O2  ⟶  MnSO4\mathrm{MnSO_3 \; + \; O_2 \; \longrightarrow \; MnSO_4} Step 3 MnSO4  +  H2O  ⟶  Mn2+  +  SO3  +  2H+\mathrm{MnSO_4 \; + \; H_2O \; \longrightarrow \; Mn^{2+} \; + \; SO_3 \; + \; 2H^+} Assume atmospheric water vapor is abundant and that hydrogen ions produced are rapidly neutralized by other processes, so their net concentration does not change. (a) Derive the overall balanced equation common to both proposed mechanisms. (b) For each mechanism separately, classify every species appearing in its elementary steps as reactant, product, intermediate, or catalyst. Present your results in two distinct tables. (c) Identify one species whose experimental detection at measurable concentration would provide decisive evidence favoring Mechanism I over Mechanism II. Justify your choice based on your classifications from part (b). (d) Propose a brief experimental approach for detecting the species identified in part (c) under realistic atmospheric conditions, and explain how the presence or absence of that species would support or refute Mechanism I.

Related theory

Browse the problem library