--- title: "Titration: Finding an Unknown Concentration" description: "Run an acid and alkali titration to a single indicator end point, then use the mole ratio in the equation to calculate the unknown concentration from concordant titres." canonical: https://lightmysky.com/learn/science/titration-finding-an-unknown-concentration-mt_7WLN35XxYx source: https://lightmysky.com/learn/science/titration-finding-an-unknown-concentration-mt_7WLN35XxYx.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Titration: Finding an Unknown Concentration Run an acid and alkali titration to a single indicator end point, then use the mole ratio in the equation to calculate the unknown concentration from concordant titres. Subject: Science · Area: Matter & Materials · Ages 15 to 16 Page: https://lightmysky.com/learn/science/titration-finding-an-unknown-concentration-mt_7WLN35XxYx ## Ready when they can - Describes the apparatus and the steps, including rinsing, swirling, and repeating until titres agree - Selects the concordant titres and takes the mean, discarding the rough run - Calculates moles from concentration and volume and crosses the mole ratio to the other reactant - Names one source of error and says which way it pushes the calculated concentration ## Lesson: Titrations that tell the truth A titration finds an unknown concentration from one you know. A burette holds acid of known concentration. A pipette measures a fixed volume of alkali, often 25.0 cm3, into a flask with a few drops of indicator. Rinse the burette and the pipette with the solutions they will hold, and rinse the flask with water. Then drip acid in with swirling until the colour flips. Run one rough titration first to find the endpoint zone. Repeat until the titres agree within 0.1 cm3. Those agreeing titres are concordant. The rough run never joins the mean. With a rough 26.0 plus 25.20, 25.25 and 25.15, drop the rough and average the rest. Add 25.20, 25.25 and 25.15 to get 75.60, then divide by 3 to get 25.20 cm3. **Example.** Turn the mean titre into an answer. Moles equal concentration times volume in dm3. Suppose 25.0 cm3 of alkali needed 20.0 cm3 of 0.15 mol/dm3 acid in a 1 to 1 reaction. Acid moles are 0.15 times 0.0200, which is 0.003. The ratio gives 0.003 mol of alkali. Divide by 0.025 dm3 to get 0.12 mol/dm3. The maths trusts the titre completely: overshoot the endpoint and the counted moles swell, so the calculated concentration comes out too high. **Tip.** Name each error and the way it pushes the result. Overshooting the endpoint inflates the titre, so the calculated concentration comes out too high. A burette rinsed with water dilutes the acid, so a bigger titre is needed and the result comes out too high as well. Technique decides accuracy, so go drop by drop near the end. **Recap.** Rinse, drip to the endpoint, average the concordant titres, and turn the mean into moles and back. ## Practice 11 questions on this page, each with its working shown. ## Needs first - [Acid Reactions & Salts](https://lightmysky.com/learn/science/acid-reactions-and-salts-mt_QKRYLwaOU8) ## Opens up - [Testing for Ions and Gases](https://lightmysky.com/learn/science/testing-for-ions-and-gases-mt_PDZjzQJdVt) - [Redox Titrations with Manganate(VII) and Thiosulfate](https://lightmysky.com/learn/science/redox-titrations-with-manganate-vii-and-thiosulfate-mt_tKZTSfo0Ra) - [Calibration, the Blank and What Makes a Measurement Trustworthy](https://lightmysky.com/learn/science/calibration-the-blank-and-what-makes-a-measurement-trustworthy-mt_UNkQFonlWJ) - [Buffers and Titration Curves](https://lightmysky.com/learn/science/buffers-and-titration-curves-mt_vevyEjNijM)