AP®ChemistryCollege BoardStudy GuidesUnit 4: Chemical ReactionsStoichiometryIntroduction to Titration

Introduction to Titration (College Board AP® Chemistry): Study Guide

Written by: Martín

Updated on 9 November 2026

Determine the concentration of an analyte

One of the most important analytical techniques is titration
Titrations include
- Acid-base titrations
- Redox titrations
The most important glass equipment used in a titration is a buret
Titrations are used to determine the concentration of a chemical compound in an unknown sample
- The unknown sample is called the analyte
The amount of analyte is determined using a solution of known concentration that reacts specifically and quantitatively (completely, in a known mole ratio) with the analyte
- The solution of known concentration is called the titrant
The buret is filled with the titrant, while the analyte is placed in an Erlenmeyer flask under the buret
The equivalence point is reached when the titrant added has exactly used up the analyte
- The moles of titrant and analyte are in the ratio given by the balanced equation
In most titrations, an indicator is added to the analyte solution
- An indicator changes color at, or very close to, the equivalence point. The observed color change is called the endpoint

Common titration setup

Titration apparatus: a buret held by a clamp above a flask. The buret, scaled 0 at the top to 50 at the bottom, is labeled 'Titrant, known concentration'; the solution in the flask is labeled 'Analyte, unknown concentration'

Titration setup: the buret holds the titrant (known concentration) and the flask holds the analyte (unknown concentration). Record the initial buret reading before you start; it does not need to be exactly 0.00 mL

How to perform a titration

Measure a known volume of analyte and place it into an Erlenmeyer flask
Rinse the buret with a small volume of the titrant and drain it, then fill the buret with the titrant (a solution of known concentration)
- Record the initial buret reading
If needed, add a few drops of indicator to the flask
Open the buret stopcock and add the titrant to the flask a little at a time
- Swirl the flask after each addition
Near the endpoint, add the titrant drop by drop
Close the buret tap when one drop has caused a permanent color change
Read the buret at the bottom of the meniscus, reading the scale from the top down, to the nearest 0.01 mL
- Volume of titrant delivered = final reading − initial reading
- Use this volume to calculate the amount of analyte

Determining the concentration of analyte

One of the most assessed calculations in AP Chemistry regarding titrations is determining the amount of analyte
The steps for this calculation are summarized in the following diagram

Steps for determining the concentration of analyte

Flow chart: mL of titrant to L of titrant (1 L over 1000 mL); to moles of titrant (M = n over V); to moles of analyte (mol analyte over mol titrant); to concentration of analyte (M = n over V)

General steps that must be followed to determine the concentration of analyte using the volume recorded from the equivalence point of the titration

Worked Example

A 30.0 mL HCl sample of unknown concentration was titrated with 0.150 M NaOH. A permanent color change was reached when adding 25.0 mL of titrant. Determine the concentration of the analyte. The balanced chemical equation is given below

HCl + NaOH → NaCl + H₂O

Answer:

Step 1: Analyze the statement and set up the steps that you are going to use to solve the problem.

Volume and molarity are both given for the titrant, NaOH, so start there

Flow chart: mL of NaOH to L of NaOH (1 L over 1000 mL); to moles of NaOH (M = n over V); to moles of HCl (1 mol HCl over 1 mol NaOH); to concentration of HCl (M = n over V)

Step 2: Calculate the moles of NaOH by transforming the volume of the equivalence point into L and using the molarity equation

$25.0 mL of solution \times \frac{1 L}{1000 mL} = 0.0250 L$

$M = \frac{n of solute}{V of solution in liters}$

Rearranging the equation,

n of solute = M × V of solution in liters

n of solute = 0.150 M × 0.0250 L

n of solute = 0.00375 mol of NaOH

Step 3: Calculate the moles of HCl that reacted using the ratio from the chemical equation

$0.00375 mol of NaOH \times \frac{1 mol of HCl}{1 mol of NaOH} = 0.00375 mol of HCl$

Since the ratio is 1:1 the moles of HCl must be the same

Step 4: Calculate the molarity of the HCl solution using the volume of the sample in L

$30.0 mL of solution \times \frac{1 L}{1000 mL} = 0.0300 L$

$M = \frac{n of solute}{V of solution in liters}$

$M = \frac{0.00375 mol}{0.0300 L}$

M = 0.125 M

Step 5: All the data are given to 3 significant figures, so give the answer to 3 significant figures

The concentration of the unknown HCl sample is 0.125 M

Examiner Tips and Tricks

Divide by the volume of the original analyte sample (here 30.0 mL), not the total volume in the flask at the end

Do not use M₁V₁ = M₂V₂ for a titration

It is the dilution equation and ignores the mole ratio
Go through moles and the balanced equation, as in Steps 2–4

Titrations are not only acid–base. In a redox titration, such as permanganate with iron(II), no base is involved

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