C1,V1 — concentration and volume of the stock solution. C2,V2 — concentration and volume of the final diluted solution.
Solving for the unknown
V2=C2C1⋅V1
Algebraic rearrangement of the dilution law to isolate the current unknown variable (V2).
Dilution Factor (DF)
DF=C2C1=V1V2
Dimensionless ratio indicating how many times the original concentration has been diluted. Fundamental for planning serial dilutions in microbiology and biochemistry.
1. Physicochemical Foundation
The equation is based on the principle of conservation of mass. When solvent is added to a solution, the amount of solute (moles or mass) remains strictly constant (n1=n2). Since the amount of solute is the product of concentration and volume (n=C⋅V), the equality follows directly.
2. The Additive Volumes Trap
Mathematically, the solvent to add is V2−V1. However, in practical laboratory analysis, volumes of real mixtures are rarely additive due to intermolecular interactions (such as hydrogen bonding). For instance, mixing 50 mL of ethanol and 50 mL of water yields ~96 mL of solution, not 100 mL, due to the contraction of partial molar volumes.
Correct technique: Never measure the solvent to add. Take the volume V1 and add solvent until you make up to volume (reach the calibration mark) of the final volume V2 in a volumetric flask.
3. Enthalpy of Mixing (ΔHmix)
The dilution of highly concentrated solutions (especially strong acids or bases) is not a thermo-neutral process. Ion hydration releases a large amount of thermal energy. To prevent localized boiling and splashing, the universal safety rule dictates that the concentrated solute must always be added slowly to a fraction of the solvent, and never the reverse.
4. Algorithmic Considerations
This suite performs predictive analysis on the inputs. If the algorithm detects that C2≥C1 or thatV2≤V1, it will issue a formal warning. Physically, increasing concentration or reducing volume requires evaporation, precipitation, or the addition of pure solute, which breaks the simple dilution mathematical modeland requires a more complex mass balance.