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Dynamic Equilibrium

01Dynamic Equilibrium

Reversible reactions

This section covers how reversible reactions proceed in both directions and how they are represented in chemical equations.

Reaction in both directions

Some reactions continue until one of the reactants has effectively been used up. In other reactions, substances formed as products can react again to produce the starting substances.

These are reversible reactions. Their equations use the symbol ⇌ to show that chemical change can proceed in either direction.

  • In the forward reaction, reactants form products.
  • In the reverse reaction, those products reform reactants.
reactants  ⇌  products\text{reactants}\;\rightleftharpoons\;\text{products}

Example of a reversible reaction

Hydrated copper(II) sulfate can form anhydrous copper(II) sulfate and water, while the reverse process can reform the hydrated solid:

CuSOX4 ⋅ 5 HX2O(s)⇌CuSOX4(s)+5 HX2O(l)\ce{CuSO4 * 5H2O(s) <=> CuSO4(s) + 5H2O(l)}

The same equation therefore represents both the left-to-right and right-to-left processes.

The symbol ⇌ shows that a reaction is reversible; it does not show that the two sides are present in equal amounts.

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