Chemical equilibrium explorer
Watch a reversible reaction reach dynamic equilibrium, then change concentration, pressure, temperature or catalyst and compare Qc with Kc as it settles again.
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Learning goals
- State that some reactions, such as making ammonia, are reversible
- Interpret data on the industrial conditions for reversible reactions, such as the Haber process
- Explain reversible reactions and dynamic equilibrium in terms of forward and reverse reaction rates
- State Le Chatelier's Principle and use it to predict how concentration, pressure or temperature changes affect a system at equilibrium
- Deduce whether concentration, pressure, temperature or a catalyst changes the value of an equilibrium constant
- Deduce the expression for the equilibrium constant Kc
- Calculate Kc from equilibrium data
- Describe and explain the conditions of the Haber process as an example of equilibrium in industry
- Dynamic Equilibrium and Le Chatelier
- Equilibrium Constants (Kc and Kp)
- Haber Process (Case Study)
[N₂] = 1.00 mol/dm³, [H₂] = 3.00 mol/dm³, [NH₃] = 0 mol/dm³ at 450 °C. Qc is less than Kc, so the forward reaction is faster.
- [N₂]
- 1.00 mol/dm³
- [H₂]
- 3.00 mol/dm³
- [NH₃]
- 0 mol/dm³
- [NO₂]
- 1.00 mol/dm³
- [N₂O₄]
- 3.00 mol/dm³
- Qc
- 0
- Kc
- 0.185
- Pressure
- 237 atm
- NH₃ at equilibrium
- 25.9 %
- Relative rate
- 0.13
Try this
0 of 5 doneLet the closed mixture reach equilibrium and compare concentrations with the two reaction rates. (not done yet)
Concentrations stay constant because the forward and backward reactions continue at equal nonzero rates.
Let nitrogen and hydrogen reach equilibrium, then add nitrogen and watch equilibrium re-establish. (not done yet)
Adding N₂ makes Qc smaller than Kc, so the forward reaction speeds up until the rates are equal again. Some of the added N₂ is used up, more NH₃ forms, and Kc is unchanged.
Squeeze the NO₂ and N₂O₄ syringe at equilibrium and watch the colour. (not done yet)
Squeezing raises every concentration, so the brown darkens at once. The mixture then shifts towards N₂O₄, which has fewer gas molecules, and the colour partly fades.
Heat an equilibrium mixture and compare Kc before and after. (not done yet)
Both forward reactions are exothermic (ΔH is negative), so heating lowers Kc and the mixture shifts left. Only a temperature change alters Kc.
In Haber conditions, compare the ammonia content and the rate at 350 °C and at 450 °C at the same pressure. (not done yet)
A lower temperature gives more ammonia at equilibrium but reaches it far more slowly. Plants use about 450 °C with an iron catalyst as a compromise, and about 200 atm because higher pressures cost more to build and run.
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