More About Le Châtelier's Principle

Henri Le Châtelier (1850-1936)

The Principle (1884)

When the state of system at equilibrium is changed, the system responds by moving in the direction (towards reactants or towards products) which minimizes the effect of the change.

The change can be an increase or a decrease in:

In Le Châtlier's Own Words:

"It is known that in the blast furnace the reduction of iron oxide is produced by carbon monoxide, according to the reaction:

but the gas leaving the chimney contains a considerable proportion of carbon monoxide,... Because this incomplete reaction was though to be due to an insufficiently prolonged contact between carbon monoxide and the iron ore, the dimensions of the furnaces have been increased. In England they have been made as high as thirty meters. But the proportion of carbon monoxide escaping has not diminished, thus demonstrating, by an experiment costing several hundred thousand francs, that the reduction of iron oxide by crbon monoxide is a limited reaction (has reached equilibrium). Acquaintance with the laws of chemical equilibrium would have permitted the same conclusion to be reached more rapidly and far more economically."

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