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

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

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

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

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

⚽ 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