Chemical Kinetics Simulator (v3)

Presets

Load a textbook example, then change rate constants or initial conditions to explore the model. Presets use well-scaled parameters for quick plots.

Simulation

Tip: Pick Δt small compared to the fastest process (rule of thumb for first-order-like kinetics: Δt ≲ 0.05 / max(k)). Increase duration until profiles level off if you need an apparent steady state.

Δt (s) Duration (s)

t = 0.000 s · Ready

Concentration vs time

Click legend entries to show or hide species

Calculation reference (student sheet)

Elementary mass-action (one reaction step)

For reactant species X_i with stoichiometric coefficients ν_i and product species Y_j with μ_j:

Forward rate: r_f = k_f ∏_i [X_i]^ν_i
Reverse rate (reversible steps): r_b = k_b ∏_j [Y_j]^μ_j
Net reaction rate: r = r_f − r_b (for irreversible steps, k_b = 0).

Species balances (single step): each reactant contributes −ν_i·r to d[X_i]/dt; each product contributes +μ_j·r to d[Y_j]/dt. Multiple steps superpose additively.

Time integration (RK4)

Let y be the concentration vector. One step of step size h = Δt:

k₁ = f(y),
k₂ = f(y + (h/2)k₁),
k₃ = f(y + (h/2)k₂),
k₄ = f(y + hk₃),
y_n+1 = y_n + (h/6)(k₁ + 2k₂ + 2k₃ + k₄).

After each accepted step, each component of y is clamped to ≥ 0 for numerical stability.

Reading the graph

Run a simulation to populate this panel. Each coloured curve is the molar concentration of one species versus time; use the legend to compare subsets or hide noisy traces.

Key data points

Sampled times along the stored trajectory (start, interior samples, end). Values match the integrator output.

t (s)
No simulation data yet.