Reaction Quotient Calculator
Calculate a user-defined concentration quotient, compare Q with known K, or derive K from concentrations at equilibrium.
A QUICK WALKTHROUGH
How to use this tool
- Choose comparison mode or calculate K from concentrations already at equilibrium.
- Enter one concentration in mol/L and its signed exponent per line, separated by a comma. Use positive exponents for products and negative exponents for reactants.
- In comparison mode, enter a matching K to calculate Q/K and direction. At equilibrium, calculate K = Q without entering K.
Calculation
Q = product of (concentration / 1 mol/L)^exponent. Signed exponents define your supplied quotient. At equilibrium, K = product of (equilibrium concentration / 1 mol/L)^signed exponent. For aA + bB ⇌ cC + dD, K = (C/1 mol/L)^c (D/1 mol/L)^d / [(A/1 mol/L)^a (B/1 mol/L)^b]. Positive exponents belong to products and negative exponents to reactants.
Model and limits
Rigorous K uses dimensionless activities; this tool approximates each activity by concentration / 1 mol/L. Use only an ideal concentration model at a specified temperature and with a consistent reaction direction and standard state. You supply the balanced-reaction exponents and decide which species to include; pure solids and liquids normally have unit activity. The tool does not balance reactions, convert pressure or activities, predict rate or experimental safety.
GOOD TO KNOW
Common questions
Is this professional guidance?
No. This is an educational calculation only. Values stay in your browser.