What is Dilution and Titration?
Dilution and titration are two fundamental laboratory techniques. Dilution decreases concentration by adding solvent; titration determines unknown concentration by reacting with a standard solution of known concentration.
Dilution uses the formula M₁V₁ = M₂V₂: initial molarity × initial volume = final molarity × final volume. Titration is an analytical method where a reagent of known concentration is added until a reaction endpoint is reached.
- 1↓StartMeasure concentrated solution (M₁V₁)
- 2↓PourTransfer to larger flask
- 3↓Add waterFill to final volume V₂
- 4↓MixStir thoroughly
- 5ResultDilute solution at M₂
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Step-by-step worked examples
If 50 mL of 4 M HCl is diluted to 200 mL, what is the new molarity?
M₁V₁ = M₂V₂ 4 mol/L × 50 mL = M₂ × 200 mL 200 = 200M₂ M₂ = 1 mol/L
To make 500 mL of 0.5 M solution from 2 M stock, how much stock is needed?
M₁V₁ = M₂V₂ 2 mol/L × V₁ = 0.5 mol/L × 500 mL V₁ = 125 mL of stock solution
In a titration, 25 mL of 0.1 M NaOH neutralized 20 mL of HCl. Find HCl molarity.
For 1:1 ratio: M_acid × V_acid = M_base × V_base M_HCl × 20 mL = 0.1 mol/L × 25 mL M_HCl = 0.125 mol/L
Flashcards
Quick quiz
Q1.20 mL of 5 M solution diluted to 100 mL. New molarity?
Q2.What does M₁V₁ = M₂V₂ describe?
Q3.To dilute a solution, you should…
Q4.In titration, the indicator shows…
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Common mistakes
Thinking dilution changes the number of moles of solute. — Correct: Dilution keeps moles constant; only concentration (and volume) change.
Using only volumes in dilution without considering molarity. — Correct: Always use M₁V₁ = M₂V₂; both molarity and volume matter.
Confusing the endpoint with the equivalence point in titration. — Correct: The endpoint is where the indicator changes; equivalence point is where moles are equal. They're close but not identical.
Adding solute instead of solvent when diluting. — Correct: Dilution adds only solvent; adding solute would concentrate, not dilute, the solution.
FAQ
What is the dilution formula and what does it mean?
M₁V₁ = M₂V₂. It shows that the moles of solute (M×V) stay the same; molarity and volume are inversely proportional.
How do I dilute a solution in the lab?
Measure the calculated volume of stock solution, pour it into a larger flask, add solvent gradually while mixing, and dilute to the mark.
What is an indicator in titration?
A dye or compound that changes color at a specific pH, marking the endpoint of the titration.
Why is titration used instead of just adding all the reagent at once?
Titration is gradual so you can detect the exact endpoint with an indicator, giving a precise and accurate result.