Collision theory

This tool uses a fixed bimolecular model reaction X+Y→products with rate law v=k[X][Y]. Concentrations are not inputs, so v is not calculated. No particular real reaction is claimed. A and k both use L mol⁻¹ s⁻¹, and A and Eₐ remain constant across the displayed temperature window.

Arrhenius calculation. k=A exp(−Eₐ/(RT)). The gas constant is R=N_Ak_B=8.31446261815324 J mol⁻¹ K⁻¹, using the exact SI defining constants. Input Eₐ is in kJ/mol; the calculation converts units consistently. The results show q=Eₐ/(RT), exp(−q), RT in kJ/mol and k. The exponential factor is a model quantity, not an observed reaction percentage. When Eₐ=0, the factor is exactly 1 and k=A.

Inputs are T=100–3000 K, Eₐ=0–300 kJ/mol and A=10⁻¹²–10²⁰ L mol⁻¹ s⁻¹. All permitted rates remain positive and finite. The graph has 241 samples from max(100,T/2) to min(3000,2T), with the selected temperature marked separately. Its vertical axis is log₁₀(k/[L mol⁻¹ s⁻¹])=log₁₀(A/[L mol⁻¹ s⁻¹])−q/ln(10). No artificial rate floor is added. A flat curve retains at least one decade of vertical range. This is neither an inverse-temperature fit nor experimental data.

Independent collision illustration. E=0–600 kJ/mol is a separate molar collision-energy parameter. The barrier comes from the last calculated Eₐ. The idealized rule is: E<Eₐ gives insufficient energy; E≥Eₐ with unfavorable orientation gives no bond; E≥Eₐ with favorable orientation permits a bond. E=Eₐ meets the energy condition, including E=Eₐ=0. Marked contact sites face each other only in the favorable orientation.

This rule is a teaching illustration, not an atomistic trajectory, success probability or predicted experimental reaction. The orientation checkbox does not multiply the calculated rate: statistical orientation effects belong to the supplied prefactor A. E and orientation affect only the illustration; T and A do not set its drawn speeds. The motion remains schematic even when E is zero.

Playback. The initial view shows the endpoint. Scrub the 0–1000 progress slider or play once over three seconds of display time: the particles approach up to halfway, then rebound or remain joined. There is no chemical time axis and no contact or reaction counter. Pause, leaving the illustration tab, hiding the tool and navigation stop playback. A delayed frame advances by at most 0.1 display seconds; hidden time is not replayed.

Input and state. Calculate is explicit. Editing T, Eₐ or A clears the old result. Invalid E clears only the illustration and disables playback, leaving a valid Arrhenius result intact. Reset retains parameters and view choices. Within-page navigation retains the result, tab and progress, paused. Reload or settings changes retain only validated parameters and view choices and require Calculate again. Plain wheel input scrolls the page.

Sources: OpenStax Chemistry 2e, 12.5 Collision Theory and the NIST fundamental constants sheet. The formulas and diagrams here are independently implemented teaching material.