The elementary gas-phase reaction
I2(g) + H2(g) → 2 HI(g)
is studied at 800 K. The total bimolecular collision frequency between I2 and H2 at this temperature is 3.2×108 collisions s⁻¹. Kinetic analysis shows that:
• Only 0.030 % of the collisions possess kinetic energy equal to or greater than the activation energy.
• Of those energetic collisions, 30 % have a geometry that allows simultaneous breaking of the H–H bond and formation of two H–I bonds.
(a) Calculate the number of collisions per second that both satisfy the energy criterion and possess a productive geometry.
(b) A catalytic surface aligns the H2 molecules so that every energetic collision now meets the geometric requirement. Assuming the energy distribution is unchanged, determine the factor by which the reaction rate is expected to increase.
(c) Describe, at the molecular level, how the catalyst could enforce the orientation specified above without altering the energy distribution.
(d) If the temperature is raised to 900 K, the fraction of collisions with sufficient energy triples while the orientation fraction (in the absence of the catalyst) remains 30 %. Calculate the new number of successful collisions per second and compare it with the catalytic case at 800 K from part (b).