CP3-CP4 UNIT 3 TITRATION

Wear eye protection. Phenolphthalein is toxic and flammable so avoid inhaling and keep away from flames. Hydrochloric acid is an irritant so avoid contact with skin. Fill the burette below eye level to avoid splashing acid into your face and eyes. Clear up spillages and broken glassware immediately.

Acid - colourless, Alkali - pink

A volumetric pipette is more accurate than a measuring cylinder.

The first point at which the indicator changes colour permanently. The point of neutralisation.

Two concordant results (within 0.10 cm³ of each other).

The rough titre is carried out at the start of the titration to gain an approximate idea of how much solution is required from the burette for neutralisation.

The rough titre is not accurate enough.

To the nearest 0.05 cm³.

To the nearest 0.05 cm³. It should match the accuracy of all the values used in the mean calculation.

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Use a pipette to add 25 cm³ of diluted HCl to a conical flask. Add a few drops of phenolphthalein. Pour sodium hydroxide into the burette. Record the initial burette volume. Complete a rough titre, swirling constantly above a white tile. Stop adding when the endpoint is reached. Record the final burette volume and calculate the volume added. Repeat until two concordant results are obtained. Use the sodium hydroxide volume to calculate moles and concentration of hydrochloric acid using the 1:1 ratio.

To ensure all the reactants are combined so that the reaction is complete.

The larger the titre volume, the smaller the percentage error.

To make the colour change easier to observe.

To make the titre volume larger so that the percentage error is smaller.

Number of moles = concentration (mol dm⁻³) × volume (dm³)

- Calculate the number of moles of the alkali using n = C × V. - Use the chemical equation to find the ratio and the moles of acid that reacted. - Divide the moles of acid by the volume used in neutralisation.

1. Weigh an empty weighing boat. Add approximately 2.5 g of sulfamic acid and reweigh the weighing boat and contents. 2. Dissolve the sulfamic acid in about 100 cm³ of water in a beaker. 3. Transfer the solution into a 250 cm³ volumetric flask. Rinse the beaker with distilled water and add the washings to the flask. 4. Make the solution up to the 250 cm³ mark on the volumetric flask.

Weigh by difference method. The weighing boat is weighed with the solid acid and then again after it is transferred to the beaker to calculate if any solid is left in the weighing boat.

Wear eye protection. Avoid ingesting sulfamic acid, wash hands after use. Fill the burette below eye level. Clear up spillages and broken glassware immediately.

Red

Yellow

Orange

A volumetric pipette is more accurate than a measuring cylinder.

The first point at which the indicator changes colour permanently.

2 concordant results (within 0.10 cm³ of each other).

It is not accurate enough.

To the nearest 0.05 cm³.

H₃NSO₃(aq) + NaOH(aq) → NaH₂NSO₃(aq) + H₂O(l).

1. Add 25 cm³ of NaOH(aq) to a conical flask with methyl orange. 2. Fill the burette with sulfamic acid. 3. Complete a trial titre, swirling constantly. 4. Repeat until two concordant results are obtained.

To ensure all the reactants are combined so that the reaction is complete.

The larger the titre volume, the smaller the percentage error.

To make the colour change easier to observe.

To make the titre volume larger so that the percentage error is smaller.

Number of moles = concentration × volume (n = C × V).

Calculate moles of acid (n = C × V), use the reaction ratio to find moles of alkali, then divide by the volume of alkali used.

Indicators are dilute weak acids and can slightly alter the solution's volume and concentration.