Reaction Quotient Calculator
Calculate reaction quotient (Q) and determine reaction direction relative to equilibrium
Calculate Reaction Quotient
Chemical Equation
Reactants
Products
Reaction Quotient Expression
Reaction Quotient Results
Formula: Q = [Products]^coefficients / [Reactants]^coefficients
Note: Pure solids and liquids have activity = 1 and are omitted from calculations
Quick Examples
Complex Formation
Cd²⁺ + 4Cl⁻ ⇌ CdCl₄²⁻
Q = [CdCl₄²⁻]/([Cd²⁺][Cl⁻]⁴)
At 25°C: K = 10⁸
Acid Dissociation
HA ⇌ H⁺ + A⁻
Q = [H⁺][A⁻]/[HA]
Compare with Ka
Gas Phase Reaction
N₂ + 3H₂ ⇌ 2NH₃
Q = P²₍NH₃₎/(P₍N₂₎P³₍H₂₎)
Use partial pressures
Understanding Reaction Quotients and Chemical Equilibrium
What is a Reaction Quotient?
The reaction quotient (Q) measures the relative amounts of products and reactants at any point during a reaction. It uses the same mathematical expression as the equilibrium constant (K) but can be calculated at any time, not just at equilibrium.
General Formula
Q = [C]c × [D]d / [A]a × [B]b
For: aA + bB ⇌ cC + dD
Predicting Reaction Direction
Q < K
Forward reaction favored. More products will form.
Q = K
At equilibrium. No net change in concentrations.
Q > K
Reverse reaction favored. More reactants will form.
Important Considerations
Pure Substances
Pure solids and liquids have activity = 1 and are omitted from Q calculations
Concentration vs Pressure
Use molarity for aqueous solutions, partial pressures for gases
Temperature Dependence
K changes with temperature, but Q is calculated from current conditions