Dilution
Definition and meaning of Dilution in chemistry.
Dilution is the process of reducing the concentration of a solute in a solution, typically by adding more solvent while the amount of solute stays constant.
In more detail
Because the moles of solute do not change during dilution, the relationship between the initial and final states is given by the dilution equation, M1V1 = M2V2, where M is molarity and V is volume. Adding solvent increases the total volume, which spreads the same number of solute particles over more space, lowering the concentration. Dilution is essential in laboratories for preparing standard solutions, titrations, and calibration curves from a concentrated stock solution, since accurately diluting a known stock is often easier and safer than weighing out small, precise masses of solute directly.
Key facts
| Key equation | M1V1 = M2V2 |
|---|---|
| What stays constant | moles of solute |
| What changes | total solution volume and concentration |
| Field | General Chemistry |
To prepare 500 mL of 0.1 M HCl from a 6 M stock solution, use M1V1 = M2V2: (6 M)(V1) = (0.1 M)(500 mL), so V1 = 8.3 mL. This volume of stock acid is measured out and then diluted with water to a final volume of 500 mL.
Frequently asked questions
Does dilution change the number of moles of solute?
No. Dilution only adds solvent; the moles of solute present remain the same before and after, which is why M1V1 = M2V2 holds.
Why should concentrated acid be added to water, not water to acid, during dilution?
Diluting concentrated acids is highly exothermic. Adding acid slowly to water keeps the acid dilute at every stage and lets the large volume of water absorb the heat, whereas adding water to concentrated acid can cause localized boiling and dangerous spattering.