Titrations | Chemistry

📖 In-Depth Theory

What Is a Titration?

A TITRATION is a technique used to find the exact volume of one solution that reacts completely with a known volume of another solution.

In acid-base titrations:

Measure the exact volume of acid needed to neutralise a known volume of alkali (or vice versa).

Used with STRONG ACIDS only at Foundation level: sulfuric acid, hydrochloric acid, nitric acid.

And STRONG ALKALIS: sodium hydroxide, potassium hydroxide.

EQUIPMENT:

BURETTE — holds the acid; accurate to ±0.05 cm³. Allows precise measurement of volume added.

PIPETTE — measures exact volume of alkali into the conical flask (e.g. 25.00 cm³).

CONICAL FLASK — holds the alkali and indicator.

INDICATOR — changes colour sharply at the equivalence point (endpoint).

Common indicators: methyl orange (yellow in alkali, red in acid), phenolphthalein (pink in alkali, colourless in acid).

WHITE TILE — placed under flask to help see colour change clearly.

Titration Procedure

STEP-BY-STEP METHOD:

1. Rinse the burette with the acid solution, then fill it. Record the initial burette reading.

2. Use a pipette to transfer exactly 25.00 cm³ of alkali into a clean conical flask.

3. Add 2–3 drops of indicator to the flask.

4. Slowly add acid from the burette — swirl flask continuously.

5. As the endpoint approaches, add acid dropwise.

6. Stop when ONE DROP causes a permanent colour change — this is the ENDPOINT.

7. Record the final burette reading. Calculate the titre (volume of acid used):

Titre = final reading − initial reading.

8. REPEAT the titration to get CONCORDANT results (results that agree within 0.10 cm³ of each other).

9. Calculate the mean titre using only concordant results — ignore any rough runs.

WHY CONCORDANT RESULTS?

Random errors affect individual readings — averaging concordant results improves reliability.

A rough titration is done first to identify the approximate endpoint — subsequent runs are more precise.

Accuracy and Reliability

SOURCES OF ERROR:

Reading the burette — parallax error (view at eye level, read from the bottom of the meniscus).

Adding too much acid past the endpoint — overshoot means the titre is too large.

Not rinsing equipment with the correct solution before use — dilutes the solutions.

Using too much indicator — can affect the endpoint reading.

IMPROVING ACCURACY:

Rinse pipette with alkali solution before use (not water — would dilute it).

Rinse burette with acid before filling.

Perform a rough titration first → do precise runs close to the endpoint.

Repeat until at least two concordant results (within 0.10 cm³).

Read burette at eye level, from the bottom of the meniscus.

CALCULATING MEAN TITRE:

Only use concordant readings — discard any outliers.

Mean = sum of concordant titres ÷ number of readings.

EXAMPLE:

Readings: 24.60, 24.55, 24.65, 25.10 cm³

Discard 25.10 (outlier). Mean = (24.60 + 24.55 + 24.65) ÷ 3 = 24.60 cm³

⚠️ Common Mistake

Only concordant results (within 0.10 cm³) are used for the mean titre — rough runs and outliers are EXCLUDED. The endpoint is when ONE DROP causes a PERMANENT colour change — stopping too early (before the colour is permanent) or adding too much gives an inaccurate titre.

📐 Key Equations

Titre = final burette reading − initial burette reading

📌 Key Note

Titration: exact volumes of acid + alkali that neutralise each other. Burette (acid) + pipette (alkali 25 cm³) + indicator + conical flask. Endpoint = permanent colour change from one drop. Concordant results within 0.10 cm³. Mean from concordant only. Discard rough run. RP Chemistry 2 (chemistry-only).

🎯 Matching Activity — Titration Equipment and Steps

Match each piece of equipment to its role in a titration. — drag the symbols on the right to match the component names on the left.

Burette

Drop here

Pipette

Drop here

Indicator

Drop here

Concordant results

Drop here

Changes colour at the endpoint — shows when the acid has exactly neutralised the alkali

Holds the acid — accurate to ±0.05 cm³, allows precise measurement of volume added

Measures a fixed volume of alkali (e.g. 25.00 cm³) into the conical flask

Two or more titres that agree within 0.10 cm³ — used to calculate the mean

⚽ FIFA Worked Examples

Mean Titre Calculation

A student records these titres: 24.85, 24.80, 24.90, 25.45 cm³. Calculate the mean titre.

F

Identify concordant results (within 0.10 cm³), discard outliers, calculate mean

I

Concordant: 24.85, 24.80, 24.90. Discard: 25.45 (outlier — differs by >0.10 cm³)

F

Mean = (24.85 + 24.80 + 24.90) ÷ 3 = 74.55 ÷ 3

A

Mean titre = 24.85 cm³

🔬 Triple Science Only

Titrations (4.4.2.5) is chemistry-only — not in Combined Science. Includes the full procedure, equipment, concordant results, calculating mean titre and sources of error.

🧪 Required Practical

🔬 RP Chemistry 2 (chemistry-only) — Determination of the reacting volumes of solutions of a strong acid and strong alkali by titration. Burette, pipette, indicator, concordant results.

Know the method, variables, equipment and how to analyse results.

🎯 Test Yourself

Question 1 of 2

1. A student records titres of 24.60, 24.55, 24.65 and 25.10 cm³. Which results should be used to calculate the mean?

2. In a titration, why is the acid added dropwise near the endpoint?

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🧪 Titrations

What Is a Titration?

Titration Procedure

Accuracy and Reliability

🔬 RP Chemistry 2 (chemistry-only) — Determination of the reacting volumes of solutions of a strong acid and strong alkali by titration. Burette, pipette, indicator, concordant results.

Mr. Badmus AI