Reaction Kinetics Lab

N₂ + 3 H₂ ⇌ 2 NH₃

Concentration per step.

Conservation (readout, not a score)

H: 6.000000 → 6.000000
N: 2.000000 → 2.000000
mass (PubChem g/mol): 34.0620 → 34.0620

Atoms are conserved exactly — which is why this is not a metric. The grams drift in the fourth digit: tabulated molar masses are rounded, and the invariant is atoms, not the table.

Reaction

Reversible, so it stops at an equilibrium rather than at exhaustion. Four molecules become two — the classic case where pressure (here: total concentration) matters.

Initial concentrations

H3N

Kinetics

Steps

Product injection (Le Chatelier)

Rate constants are chosen for legibility, not taken from literature. There is no temperature control: the constants are the controls.

Metrics

Total357 / 500

SETTLING100

What is settling?

Established physics

Has the reaction stopped changing? At the start things move fast; as reactants run low or products build up, the net change slows. This is how close to still the mixture is by the end, compared with its fastest moment.

Try — Halve the number of steps and watch settling fall — the reaction was still moving when you stopped looking. Then double kf: it settles sooner, and stability starts to care.

Atkins & de Paula — Physical Chemistry, ch. "The rates of chemical reactions" and "Chemical equilibrium"

CONVERSION65

What is conversion?

Established physics

How much of the reactant that runs out first was actually used up. 100 means it is gone; a reversible reaction stops short of that, because products push back.

Try — On the Haber preset, add hydrogen beyond 3:1 and watch nitrogen conversion rise without touching the rate constants. That is Le Chatelier from the reactant side.

Atkins & de Paula — Physical Chemistry, ch. "The rates of chemical reactions" and "Chemical equilibrium"

STABILITY100

What is stability?

Established physics

The simulation takes fixed-size steps. If a step is too big for how fast the reaction runs, concentrations overshoot, swing back and forth, and can even go below zero — which is not chemistry, it is the arithmetic failing.

Try — Raise dt until this collapses. The value where it goes is the stability boundary of the method, and it moves when you change kf — the safe step size belongs to the reaction, not to the module.

Atkins & de Paula — Physical Chemistry, ch. "The rates of chemical reactions" and "Chemical equilibrium"

LE CHATELIER0

What is le chatelier response?

Established physics

Halfway through, the module dumps extra product into the mixture. A reversible reaction pushes back — converts some product into reactants again until the ratio is restored. This scores how much of that push-back happened.

Try — Set a perturbation on NO₂ ⇌ N₂O₄ and watch Q spike then fall back toward K. Then try the same on hydrogen + oxygen: nothing comes back, because nothing can.

Atkins & de Paula — Physical Chemistry, ch. "The rates of chemical reactions" and "Chemical equilibrium"

PACE92

What is pace?

Computational experiment

How quickly the reaction got most of the way to where it ends up. A reaction that reaches 95% of its final conversion early scores high; one still crawling at the end scores low.

Try — Push kf and dt up together. Pace climbs until stability breaks, and the pair of them finds the edge for you — the same edge Causal Forge finds with α.

Stability grades the numerical method, not the chemistry: a good mechanism at a careless step size scores 0 here and high on conversion at once — the two readings together are the lesson.

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Mix, wait, and watch the ratio settle.

Four real reactions — species data from PubChem, recorded with their compound ids — run under mass-action kinetics: every rate is a product of concentrations and a constant. Reversible ones stop at an equilibrium where the reaction quotient Q equals K = kf/kr; a one-way reaction stops when something runs out. Inject product mid-run and watch Le Chatelier's principle push the ratio back.

The integrator is a fixed explicit-Euler step, and its stability edge is part of the game: raise the rate constants or the step and the arithmetic overshoots, oscillates, and finally produces concentrations below zero. Stability grades that, and nothing else — the same lesson Causal Forge teaches with α, in a second science.

A toy in its own units: no temperature, no solvent, no activity coefficients, and rate constants chosen for legibility rather than taken from literature. The mechanism is the real one; the numbers are not anyone's measurements. Atom conservation is exact by construction and is therefore shown, not scored.