Titrations

 Learning how to do titrations. Allowing students to repeat the experiments multiple times helps them develop the skills necessary to perform titrations accurately. Titrating is a skill that many students need to practice repeatedly to acquire the ability to do it accurately and with precision.

How to Perform a Titration – Neutralising an Acid or Base

Titration is one of the most iconic and satisfying experiments in the chemistry lab. It's a simple but powerful technique used to determine the concentration of an acid or base by neutralising it with a solution of known concentration. In this post, we’ll walk through the step-by-step method for a titration, explain the chemistry behind it, and highlight which indicators to use depending on the type of acid and base involved.

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🔬 What Is a Titration?

A titration is a quantitative chemical analysis method used to determine the concentration of a substance in a solution. In a neutralisation titration, you slowly add an acid to a base (or vice versa) until the reaction is complete. This point is known as the equivalence point.

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🧪 Equipment You’ll Need

• Burette

• Clamp and stand

• Conical flask

• Pipette and pipette filler

• Beaker

• White tile (to better see colour changes)

• Acid (e.g., hydrochloric acid)

• Base (e.g., sodium hydroxide)

• Indicator (e.g., phenolphthalein or methyl orange)

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⚗️ Step-by-Step: How to Perform a Titration

1. Rinse your apparatus

   • Rinse the burette with the acid and fill it.

   • Rinse the pipette with the alkali (base) and use it to transfer a measured volume (e.g., 25.0 cm³) to the conical flask.

   • Rinse the conical flask with distilled water only.

2. Add the indicator

   • Add a few drops of a suitable indicator to the conical flask.

3. Set up the apparatus

   • Place the conical flask on a white tile under the burette.

   • Ensure the burette is clamped vertically and that the nozzle is over the flask.

4. Perform a rough titration

   • Open the burette tap slowly and swirl the conical flask gently.

   • Note the point at which the indicator changes colour. This is your rough estimate.

5. Repeat for accuracy

   • Refill the burette if necessary and do more titrations.

   • This time, add the acid drop by drop as you approach the rough volume.

   • Record the final burette readings and calculate titre values (volume of acid used).

   • Repeat until you get concordant results (within ±0.1 cm³ of each other).

6. Calculate the concentration
   Use the titration formula:

   $$\text{C₁V₁ = C₂V₂}$$

   Where:

   • C₁ = concentration of known solution

   • V₁ = volume of known solution used

   • C₂ = concentration of unknown

   • V₂ = volume of unknown used

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🎨 Choosing the Right Indicator

Different indicators change colour at different pH values. The key is to choose an indicator that changes colour as close as possible to the equivalence point of the reaction.

Indicator	Colour in Acid	Colour in Alkali	Best For
Phenolphthalein	Colourless	Pink	Strong base + weak acid
Methyl orange	Red	Yellow	Strong acid + weak base
Litmus	Red	Blue	Not suitable for titration
Universal indicator	Multiple colours	Multiple colours	Not used in accurate titrations

Example:

• Hydrochloric acid (strong) + sodium hydroxide (strong) → Use phenolphthalein or methyl orange

• Ethanoic acid (weak) + sodium hydroxide (strong) → Use phenolphthalein

• Hydrochloric acid (strong) + ammonia (weak) → Use methyl orange

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🧠 Top Tips

• Always take initial and final burette readings to calculate the volume added.

• Swirl continuously to ensure mixing.

• Use a white tile to clearly see the colour change.

• Don’t forget to record all readings to 2 decimal places, ending in .00 or .05.

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🧾 Real-World Applications

• Food industry: Checking acidity in wine or vinegar.

• Medicine: Calculating correct dosages for drugs.

• Environmental science: Measuring acidity in rainwater or lakes.

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✅ Summary

Titration is a precise, practical way to uncover the mystery of an unknown concentration. Whether you’re a student or a seasoned chemist, mastering this technique gives you insight into the heart of analytical chemistry. With the right indicator and a steady hand, you can turn a clear liquid into colourful data!