The quantum casino: simulations
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Equilibrium mixtures

This simulation lets you investigate some real reversible reactions – many of them important industrially. Add a reaction 'by hand' by setting reactants, products and K, or else choose a reaction from the Reaction library. By dragging any of the tops of the blue (or black in the monochrome colour scheme) rectangles on either side of the equilibrium you can adjust the intial concentrations of the reactants or products and observe using the adjacent red (or white in monochrome) rectangles their concentrations after equilibrium has been established. You can also look at how the temperature affects the equilibrium position for reactions in which ∆H is either negative or positive. It is also possible to use the slider to artificially increase or decrease the equilibrium constant. (In reality this can only be done by changing the temperature.)

Set reaction or choose from the library below

reactants products K  


colour scheme: monochrome | blue and red

Reaction library

Reaction ∆H / kJ mol-1 Temperature / K
N2O4(g) 2NO2(g) +58  298 | 350 | 400 | 450 | 500 | 550 | 600
N2(g) + 3H2(g) 2NH3(g) –100 298 | 400 | 500 | 600 | 700 | 800 | 900
H2(g) + CO2(g) H2O(g) + CO(g) +40 298 | 500 | 700 | 800 | 900 | 1000 | 1100
2SO2(g) + O2(g) 2SO3(g) –197 298 | 500 | 700 | 1100
H2(g) + I 2(g) 2HI(g) +27 298 | 500 | 700 | 764 | 1100



You should have noticed that for reactions with a positive value of ∆H (ie those that absorb heat from the surroundings heat on going from left to right), increasing the temperature increases the amount of product. In other words the reaction responds to being heated by absorbing heat. For reactions with a negative value of ∆H, the reverse occurs.

Increasing the initial concentration of one or more of the reactants results in more product in the equilibrium mixture.

Both these effects can be summed up in Le Chatelier’s principle which states that if a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance.

The quantum casino