Beginner Topic 462 of 1102 Kinetics & Equilibrium
Reversible Reactions
Reactions that can proceed in both directions toward an equilibrium.
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In-depth explanation of Reversible Reactions
A reversible reaction is one in which the products can react to re-form the reactants, so forward and reverse processes occur at the same time. The net rate is the difference between the forward and reverse rates, which for a simple reaction A <-> B is the forward rate constant times [A] minus the reverse rate constant times [B]. Because of this competition, the reaction approaches a state of equilibrium from either direction and does not go to complete conversion unless one product is removed. Most chemical reactions are reversible to some extent, and recognizing this is essential for predicting product yields.
Going deeper: Reversible Reactions
Key ideas: For A <-> B with first order steps, net rate = kf[A] - kr[B] and the approach to equilibrium is exponential with relaxation rate kf + kr. The time to equilibrium is therefore set by the sum, not the difference, of the two constants. At equilibrium K = kf/kr, so a favourable reaction has kf much greater than kr.
Common mistakes and connections: Students think a reversible reaction stops when it reaches equilibrium, or that the reverse reaction begins only after the forward one finishes. Both proceed from the start. Another mistake is using the simple integrated law of the forward reaction late in the run, where the reverse rate is no longer negligible. Related topics are dynamic equilibrium and relaxation methods.
Visualization of Reversible Reactions
Forward and reverse rates compete: the net rate falls to zero as the mixture settles at a composition fixed by K, reachable from either side. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Dinitrogen tetroxide and nitrogen dioxide interconvert, N2O4 <-> 2NO2, and both are present at equilibrium.
Frequently asked questions about Reversible Reactions
What is Reversible Reactions?
Reactions that can proceed in both directions toward an equilibrium.
Is Reversible Reactions a beginner, intermediate or advanced topic?
Reversible Reactions is a beginner topic in Kinetics & Equilibrium. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Reversible Reactions?
Study these earlier topics in Kinetics & Equilibrium first: Oscillating Reactions, Photochemical Reactions, Quantum Yield.
What comes after Reversible Reactions?
The next topics in Kinetics & Equilibrium are Dynamic Equilibrium and Equilibrium Constant.
Can I practise Reversible Reactions with quizzes?
Yes. The interactive lesson includes a self-check question on Reversible Reactions, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Reversible Reactions fits in Kinetics & Equilibrium
Reversible Reactions is topic 43 of 91 in Kinetics & Equilibrium.