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Ammonia Synthesis

High schoolChemistryIdeal-gas isobaric ammonia equilibrium from constant standard enthalpy and entropy, with illustrative relaxation kinetics

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About this experiment

Explore the tradeoff between ammonia equilibrium yield and approach speed. Change pressure, temperature and feed ratio, then compare what adding a catalyst changes and what it leaves fixed.

Learning goals

  • Relate pressure to the reduction in total gas moles during ammonia synthesis.
  • Separate equilibrium conversion from finite-time conversion.
  • Distinguish a catalyst effect on rate from an equilibrium shift.

How to use it

  1. 1Run the default reactor and compare actual with equilibrium conversion.
  2. 2Increase pressure at the same temperature and feed ratio.
  3. 3Lower temperature and compare the higher equilibrium yield with the slower approach.
  4. 4Add the catalyst and verify unchanged equilibrium conversion with faster finite-time production.

The model

The constant-enthalpy and constant-entropy approximation sets equilibrium.
The equilibrium extent satisfies Q p equal to K p at the selected total pressure.
The separate relaxation model illustrates finite-time approach without claiming detailed reaction kinetics.

Assumptions

  • The feed contains one mole of N₂ and the selected H₂-to-N₂ ratio, with no initial ammonia. Pressure is held constant in an ideal-gas model.
  • Constant standard enthalpy minus 92.22 kilojoules and entropy minus 198.75 joules per kelvin approximate the equilibrium constant for the reaction as written. Heat-capacity changes and gas nonideality are omitted.
  • A phenomenological exponential relaxation approaches the computed equilibrium extent. Its Arrhenius rate scale is illustrative, and the catalyst multiplies it by eight.
  • The apparatus is not an industrial reactor or safety-design model. Molecule samples illustrate composition; numerical inventories conserve nitrogen and hydrogen atoms exactly.

Try this in class

  1. Q1Why does higher pressure favour ammonia in this ideal-gas model?
  2. Q2Why can a catalyst improve finite-time conversion while leaving the equilibrium limit unchanged?

Frequently asked questions

Are the displayed yields precise industrial predictions?

No. The ideal-gas and constant-thermodynamic-property approximations isolate trends and omit important high-pressure and heat-capacity effects.

Does the catalyst alter the thermodynamic equilibrium constant?

No. It changes only the illustrative relaxation rate and leaves the computed equilibrium extent unchanged.