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Chemistry
Dynamic Chemical Equilibrium
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Watch N₂O₄ split into NO₂ as NO₂ combines again. Change temperature, drag the piston or add a substance to explore a new equilibrium.
The gas is reacting. Try dragging the piston to compress it.
Model time τ τ 0.0
N₂O₄ ⇌ 2NO₂
1.00 L
Drag to compress the gas
vt > vn · shifts forward
Gas colour
colorlessreddish brown
Magnified representatives · not actual counts
Add or remove a substance
N₂O₄±0.5 mmol per press
NO₂±1.0 mmol per press
NO₂: There is not enough of this substance to remove a full dose.
What does each control do?
Drag the handle on the chamber or use the slider.
Changing temperature changes Kc and both reaction rates.
Each dose: 0.5 mmol N₂O₄ or 1.0 mmol NO₂.
Same 25 °C, 1.00 L and the same amounts of N and O atoms. Restarts time and keeps the pinned reference.
Concentration
mmol/LN₂O₄5.000 mmol/LNO₂0.000 mmol/L
1050
0246
Time τ
Reaction rates
mmol/(L·τ)ForwardReverse
10.50
0246
Time τ
Press Run simulation to reveal the changing curves.
Both rates use the same reaction-extent basis.
Pin a reference, change the conditions, then compare the results.
Look deeper: amounts and Qc/Kc
Qc < Kc: the forward reaction is faster, producing more NO₂.
- Reaction quotient Qc
- Equilibrium constant Kc
- n(N₂O₄)
- 5.000 mmol
- n(NO₂)
- 0.000 mmol
- Pressure
- 0.124 bar
- Total NO₂ units
- 10.000 mmol
Qc = ([NO₂]/c°)² ÷ ([N₂O₄]/c°), c° = 1 mol/L. Qc and Kc are dimensionless.
Concentration = amount ÷ volume. Equilibrium does not require equal amounts of both substances.
τ is model time, not the duration of a real experiment.
Model notes
- The model represents one gas equilibrium, N₂O₄(g) ⇌ 2NO₂(g), in an ideal, well-mixed, temperature-controlled chamber. Condensation, side reactions and heat loss are omitted.
- Equilibrium constants use NIST thermodynamic data at 298.15 K, approximating ΔH° = 57.12 kJ/mol and ΔS° = 175.70 J/(mol·K) as constant from 15 to 50 °C. This is an approximate model, not an experimental measurement.
- Both rates use the same reaction-extent basis. Kinetic parameters are chosen for observation; τ and playback speed do not predict real reaction times.
- Molecules are representatives, not actual counts. Splitting and joining illustrate both reaction directions. Gas colour indicates NO₂ concentration at a fixed optical depth; it is not a calibrated spectroscopy scale.
- Dragging the piston is treated as an instantaneous volume change at fixed temperature; changing temperature holds volume fixed. Selective addition or removal is an ideal investigation tool. The scene is not a procedure for handling real chemicals.
- The Dynamic equilibrium label uses a 1% rate difference threshold for 0.5 τ. Reactions continue and amounts are not forced to a preset equilibrium value.