Is a hard enough collision always enough?
"Is a hard enough collision always enough?" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the NCERT section "Collision theory" in Chemical Kinetics. A 2D box of moving A and B discs; each collision is checked for energy ≥ Ea and for the right approach angle, giving Z, the energetic fraction and the steric factor P. NEET has asked about this idea 1 time in 10 years of papers. JEE Main asked 48 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Collision theory in Chemical Kinetics. Change the values and watch what happens.
What it shows
NCERT §3.5
A 2D box of moving A and B discs; each collision is checked for energy ≥ Ea and for the right approach angle, giving Z, the energetic fraction and the steric factor P.
Controls
4 to try
- Slidertemperature 250–500 K
- Slideractivation energy 20–80 kJ mol⁻¹
- Sliderallowed approach cone 10–360° (steric factor)
- Readoutscollisions/s, energetic fraction e^(−Ea/RT), effective collisions/s
Try this
Set the cone so only about one in five energetic collisions reacts (P ≈ 0.2), then raise T by 10 K and see the effective rate roughly double.
Common mistake
Every collision with enough energy leads to reaction.
In NEET
10 years of papers
Asked 1 time in 10 years of NEET.
See the past questions: Chemical Kinetics, Chemical Kinetics (chapter)
In JEE Main
42 shifts analysed
48 questions from Chemical Kinetics across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT §3.5
- Collision theory (Max Trautz and William Lewis, 1916-18) treats molecules as hard spheres and says a reaction happens only when molecules collide.
- Collision frequency Z counts how many collisions happen each second in a unit volume of the reacting mixture.
- Only collisions carrying at least a threshold energy can succeed. Threshold energy = activation energy + energy the molecules already have.
- For A + B → products, rate = Z_AB e^(−Ea/RT), where e^(−Ea/RT) is the fraction of collisions energetic enough to react. This mirrors the Arrhenius equation, with Z_AB in the role of A.
- Proper orientation is also needed: for the formation of methanol from bromomethane and OH⁻, the OH⁻ must approach the carbon on the side away from bromine, or the collision fails even with enough energy.
- Energy and orientation together make an effective collision. Adding a probability (steric) factor P gives rate = P Z_AB e^(−Ea/RT).
- The theory's weakness is its hard-sphere picture of atoms and molecules; it ignores their structure, which is why P is needed at all.
Questions
5 answers
- What does the "Is a hard enough collision always enough?" simulation show?
- A 2D box of moving A and B discs; each collision is checked for energy ≥ Ea and for the right approach angle, giving Z, the energetic fraction and the steric factor P.
- What mistake does the "Is a hard enough collision always enough?" simulation fix?
- A common mistake it clears up: every collision with enough energy leads to reaction.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 1 time in 10 years of papers.
- Does JEE Main ask questions from Chemical Kinetics?
- Yes. JEE Main asked 48 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Collision theory" in Chemical Kinetics (Class 12 Chemistry).
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