Dilution Equation
Relates concentration and volume before and after dilution.
Formula
Variables
Example
Diluting 10 mL of 6 M acid to 60 mL gives 6·10/60 = 1 M.
How it works
This equation works because dilution does not change the amount of solute, only the amount of solvent around it. So the initial amount of dissolved substance, found by concentration × volume, must equal the final amount after water or another solvent is added. As the volume increases, the concentration drops in direct proportion.
When to use it
Use this when a solution is diluted by adding solvent, such as in lab preparations, medicine dosing, or making weaker cleaning or chemical solutions. It is useful whenever you know three of the four values and need the missing one.
Worked example, step by step
A student has 25 mL of a 4 M sugar solution and dilutes it to 100 mL. Use C1V1 = C2V2 (4 M)(25 mL) = C2(100 mL) 100 = 100C2 C2 = 1 M Final answer: the diluted solution has a concentration of 1 M.
Common mistakes to avoid
- Using the formula when solute is added or removed, not just diluted
- Mixing units, such as mL for one volume and L for the other without converting
- Solving for the wrong variable or swapping the initial and final concentrations
Did You Know?
"Add acid to water, never water to acid" — the dilution can release enough heat to spatter dangerously.
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