ZornScience

Equilibrium Sandbox

How to use this lab

Start at equilibrium, predict a shift, then change one condition and watch the system respond.

  1. Disturb the reaction. Add or remove N₂O₄ or NO₂. Watch the concentrations jump and then settle to a new equilibrium.
  2. Change the volume. Compress or expand the vessel. Predict which direction is favored by the number of gas molecules.
  3. Change the temperature. The forward reaction is endothermic. Compare the new Kc with the value at 298 K.
  4. Explain the evidence. Compare Qc with Kc and use the live graph. Pause to inspect a change; Reset experiment starts fresh.
Try a compression

Reduce the volume from 5 L to 2 L. Both concentrations rise immediately, then the reaction shifts toward N₂O₄, the side with fewer gas molecules.

Download your data as CSV or print the lab. This idealized model uses accelerated time for learning.

Le Chatelier’s stress sandbox

A system under stress

N₂O₄(g) ⇌ 2 NO₂(g) ΔH° = +57.2 kJ/mol

02 / OBSERVE THE SYSTEM

The reaction vessel

VARIABLE-VOLUME REACTORIDEAL GAS MODEL

Blue atoms: N · amber atoms: O   /   Schematic molecule counts

03 / FOLLOW THE RESPONSE

Concentration vs. time

━ N₂O₄   ┅ NO₂ · vertical dotted lines mark disturbances

Investigate & understand the model
  1. At 298 K, add N₂O₄. Predict the shift before watching the graph.
  2. Compress the vessel. Why do both concentrations jump before the reaction shifts left?
  3. Heat the system. Explain why an endothermic forward reaction has a larger Kc.

Kc = [NO₂]²/[N₂O₄]. Qc uses the current concentrations. Qc < Kc favors products; Qc > Kc favors reactants. Equilibrium means equal forward and reverse rates, not equal concentrations.

Ideal-gas, constant-temperature relaxation model. Kc = 0.150 at 298 K; van ’t Hoff temperature dependence uses constant ΔH°. Simulated seconds are illustrative, not measured kinetics. Pressure uses P = nRT/V.