Beginner Topic 472 of 1102 Kinetics & Equilibrium
Effect of Concentration on Equilibrium
Adding reactant shifts equilibrium to products; removing product has the same effect.
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In-depth explanation of Effect of Concentration on Equilibrium
When the concentration of a reactant is increased or the concentration of a product is decreased, the reaction quotient Q falls below K and the equilibrium shifts to the right to form more products. Conversely, removing a reactant or adding a product shifts the equilibrium to the left. The shift continues until Q again equals K, at which point the system has a new equilibrium composition. The value of K itself does not change in these cases, because the temperature is unaltered. This principle is widely used in industry to drive reactions to completion by continuously removing the product.
Going deeper: Effect of Concentration on Equilibrium
Key ideas: After adding reactant, Q drops below K, so net forward reaction occurs until Q = K again. At the new equilibrium, the added reactant is only partly consumed, while the products are higher than before. The ratio of concentrations stays fixed through K, so check by recalculating Q after each change. Removing product continuously, as in distillation, can force high conversion.
Common mistakes and connections: Students think the reactant concentration returns to the old value, or that K changes when concentration changes. The concentration of the added species ends higher than the original value but lower than right after addition. Another mistake is adding a pure solid or liquid and expecting a shift, which does not happen. Links to Le Chatelier, ICE tables and the common ion effect.
Visualization of Effect of Concentration on Equilibrium
Adding Fe3+ at the marked time makes Q fall below K, so more red FeSCN2+ forms until a new equilibrium is reached; K itself is unchanged. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Adding Fe3+ ions to a solution containing FeSCN2+ shifts the equilibrium to form more of the red complex, intensifying its colour.
Frequently asked questions about Effect of Concentration on Equilibrium
What is Effect of Concentration on Equilibrium?
Adding reactant shifts equilibrium to products; removing product has the same effect.
Is Effect of Concentration on Equilibrium a beginner, intermediate or advanced topic?
Effect of Concentration on Equilibrium is a beginner topic in Kinetics & Equilibrium. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Effect of Concentration on Equilibrium?
Study these earlier topics in Kinetics & Equilibrium first: Manipulating K, ICE Tables, Le Chatelier's Principle.
What comes after Effect of Concentration on Equilibrium?
The next topics in Kinetics & Equilibrium are Effect of Pressure on Equilibrium and Effect of Temperature on Equilibrium.
Can I practise Effect of Concentration on Equilibrium with quizzes?
Yes. The interactive lesson includes a self-check question on Effect of Concentration on Equilibrium, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Effect of Concentration on Equilibrium fits in Kinetics & Equilibrium
Effect of Concentration on Equilibrium is topic 53 of 91 in Kinetics & Equilibrium.