Chemistry 30 Chemical Kinetics

Which one of the following reactions would you expect to be fastest at room temperature and why?

	Solution:
Pb²⁺_(aq) + 2 Cl^-_(aq) →PbCl_{2 (s)}	fastest - ions in aqueous solution react very quickly; all are in the same phase
Pb_(s) + Cl_{2 (g)} → PbCl_{2 (s)}	slower - one of the reactants is a solid

Consider the following reactions. Which do you predict will occur most rapidly at room conditions? Slowest?

	Solution:
C₂H_{6 (g)} + O_{2 (g)} → 2 CO_{2 (g)} + 3 H₂O_(g)	slow due to covalent bonding (unless the reaction is highly exothermic)
Fe_(s) + O_{2 (g)} → Fe₂O_{3 (s)}	slowest - solid reactant (Fe); this reaction describes the rusting of iron
H₂O_(l) + CO_{2 (g)} → H₂CO_{3 (g)}	slow due to covalent bonding
2 Fe³⁺_(aq) + Sn²⁺_(aq) → 2 Fe²⁺_(aq) + Sn⁴⁺_(aq)	fastest - ions in solution react very quickly

Chemistry 30