Explore how concentration changes reaction rate through particles, equations and graphs.
Initial rate mol dm⁻³ s⁻¹
Condition A
Particles show balanced reactant-to-product changes, with intermediate steps omitted. Use Start both conditions to run the reaction with any graph selected. The time slider lets you inspect a specific moment. Set initial concentrations before starting. Reset unlocks both conditions for a new comparison. Motion and sizes are illustrative.
Condition B
Particles show balanced reactant-to-product changes, with intermediate steps omitted. Use Start both conditions to run the reaction with any graph selected. The time slider lets you inspect a specific moment. Set initial concentrations before starting. Reset unlocks both conditions for a new comparison. Motion and sizes are illustrative.
Condition A
Add NH₃ through a sealed inlet into a fixed-volume vessel.
Condition B
Add NH₃ through a sealed inlet into a fixed-volume vessel.
Condition A graph
Condition B graph
Save up to four points, then change concentration to compare the rates. Saved points last until you change reaction model or reset.
The platinum view shows adsorption followed by the overall change 2NH₃ → N₂ + 3H₂, freeing sites for further reaction. Both closed vessels retain products and run at the same reaction time. Initial concentrations are locked after starting. The graph describes the selected initial concentration, while the animation illustrates subsequent consumption. Reset prepares both samples again. Elementary catalytic steps are omitted. Particle motion is schematic.
Rate–concentration graphs compare separate initial-rate experiments. In the two-reactant mode, hold [B] constant while varying [A], or hold [A] constant while varying [B]. The balanced equation alone does not determine reaction order.
The second-order straight-line graph uses [A]² on the horizontal axis. The rate–[A] graph is curved. Log graphs use log₁₀ of numerical values in the displayed mol dm⁻³ and mol dm⁻³ s⁻¹ units; zero is excluded.
The concentration–time model assumes A → products and rate = −d[A]/dt, constant volume and fixed k. The zero-order model ends at depletion. Time curves and log graphs are included for exploration; no half-life calculation is required.
Ammonia decomposition on platinum: 2NH₃(g) → N₂(g) + 3H₂(g). Drag [NH₃] to fill the surface. This simplified teaching model uses an illustrative saturation concentration of 0.80 mol dm⁻³. Rate rises before saturation. Once saturated, the graphs switch entirely to the zeroth-order law, rate = k; this law applies only while the surface remains saturated. Real adsorption changes smoothly; the sharp threshold and numerical values are not experimental data. Temperature and exposed Pt area are fixed.
Temperature and k are held constant within each example. The units of k depend on the overall order. Model values are simulated.