Neutralisation GCSE Chemistry Practical

Determination of the reacting volumes of solutions of a strong acid and a strong alkali by titration.

The required practical activity can be adapted for students of higher and lower tiers of entry. Students are assessed on their ability to use appropriate laboratory apparatus to make accurate measurements. Students will use a burette and a colour-changing indicator to investigate what volume of Sulfuric Acid will neutralise 25mls of Sodium Hydroxide.

Equipment (per participant)

• Safety goggles
• 250ml conical flask
• 25ml volumetric pipette
• Pipette filler
• Burette funnel
• Burette holder

• Retort stand
• White tile
• Sodium Hydroxide (0.1M)
• Sulfuric Acid (0.08M)
• Phenolphthalein Indicator

Method

Preparation and Setup

Gather Equipment

Collect all necessary equipment, including a burette, burette holder, retort stand, graduated glass pipette, pipette filler, 250ml conical flask, 100ml beaker, white tile, funnel, and phenolphthalein indicator.

Set Up the Burette

Secure the burette in the holder on the retort stand, ensuring the burette tap is closed.
Pour Sulfuric Acid into a 100ml beaker to make it easier to fill the burette.
Place the funnel in the top of the burette and carefully fill it with Sulfuric Acid until the level is slightly above the maximum volume line.
Remove the funnel and slowly release some acid by opening the tap, ensuring the meniscus aligns exactly with the maximum volume mark.
Discard the excess acid collected in the 100ml beaker.

Prepare the Sodium Hydroxide Solution

Use the graduated pipette and pipette filler to measure exactly 25ml of Sodium Hydroxide solution.
Transfer the Sodium Hydroxide into a 250ml conical flask.
Add 5–10 drops of phenolphthalein indicator to the Sodium Hydroxide solution and swirl to mix thoroughly. The solution should turn pink.

Positioning for the Experiment

Place the conical flask on a white tile directly underneath the burette.

Performing the Titration

Initial Dispensing

Using the burette tap, carefully dispense 10ml of Sulfuric Acid into the conical flask while swirling it continuously.

Controlled Addition

Adjust the tap to add Sulfuric Acid one drop at a time while continuing to swirl the flask.
Stop adding acid as soon as the pink colour disappears permanently, indicating the solution has been neutralized.

Record Results

Read the volume of acid used from the burette scale, ensuring the value is recorded to two decimal places in a suitable table.

Repeating the Experiment

Repeat for Accuracy

Repeat the entire titration process two more times, recording the results each time.
Calculate the mean volume of Sulfuric Acid used from the three trials.

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Technician tips

• Always consult the CLEAPSS method for diluting concentrated acids. 0.08M Sulfuric Acid is made up wearing splash-proof goggles or face shield and chemical resistant gloves. 4.32mls of concentrated sulfuric acid is slowly and carefully added to 200mls of iced water on a magnetic stirrer. Once the ice has melted, the solution is then made up to 1 Litre.
• Always consult the CLEAPSS method for making a solution of Sodium Hydroxide. Wearing appropriate PPE, 4g of Sodium Hydroxide pellets are dissolved in 1 Litre of water to make a 0.1M solution