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Reaction Quotient Q and K
Build the concentration quotient from a balanced equation, calculate Q and compare it with K to determine the direction of the net change toward equilibrium.
The equation is balanced automatically. Pure solids (s) and pure liquids (l) are excluded by default; you can change each checkbox.
N₂ + 3 H₂ ⇌ 2 NH₃
With [N₂] = 1, [H₂] = 3 and [NH₃] = 2, the quotient is Q = [NH₃]² / ([N₂][H₂]³) = 4/27 ≈ 0.148. If K = 10, then Q < K, so the net change tends toward products.
Reading Q compared with K
If Q < K, the composition must move toward products to reach equilibrium. If Q > K, it must move toward reactants. When Q = K, the system is at equilibrium.
The mathematical form depends on the chosen equilibrium constant. This page treats the entered values as the terms of a concentration quotient. Pure solids and liquids are normally omitted from the expression because their activities are taken as constant.