Acid- Base titrations (Cambridge O Level Chemistry)

The following paragraph was taken from a student’s notebook.

To make potassium chloride

25.0 cm³ of aqueous potassium hydroxide were placed in a flask and a few drops of indicator were added. Dilute hydrochloric acid was added to the flask until the indicator changed colour. The volume of acid used was 19.0 cm³.

What piece of apparatus should be used to measure the aqueous potassium hydroxide? 

Which solution was more concentrated? Explain your answer.

How could pure crystals of potassium chloride be obtained from this experiment? 

A student investigated the reaction between two different solutions of dilute hydrochloric acid, A and B, and solution C which is alkaline.

Two experiments were carried out

Experiment 1

A burette was filled with solution A of dilute hydrochloric acid to the 0.0 cm³ mark. Using a measuring cylinder, 20 cm³ of solution C was poured into a conical flask. A few drops of methyl orange were added to the flask.

Solution A was added to the flask, with shaking, until the mixture just changed colour. Use the burette diagram to record the burette reading in the table and complete the table.

Experiment 2

The burette was emptied and rinsed, first with distilled water, and then with a little of solution B. The burette was filled with solution B of dilute hydrochloric acid to the 0.0 cm³ mark.

Experiment 1 was repeated using solution B.

Use the burette diagram to record the burette reading in the table and complete the table.

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Why was the burette rinsed, first with distilled water and then with solution B, before starting Experiment 2?

Separate: Chemistry and Extended Only 

Separate: Chemistry and Extended Only

If Experiment 2 was repeated using 10 cm³ of solution C, what volume of dilute hydrochloric acid would be used? Explain your answer. 

Separate: Chemistry Only

Give one advantage and one disadvantage of using a measuring cylinder for solution C.

Describe a method other than titration, using a different reactant, that could be used to compare the concentrations of the two solutions of dilute hydrochloric acid, A and B.

A chemist used a volumetric pipette to add 25.0 cm³ of a solution of sodium hydroxide of unknown concentration to a conical flask.

The chemist then carried out a titration to find out the volume of 0.150 mol / dm³ sulfuric acid needed to neutralise the sodium hydroxide.

Describe how the chemist would complete the titration.

You should state a suitable indicator and give the colour change that would be observed.

Explain why a pipette would be used to measure the sodium hydroxide solution but a burette would be used to measure the sulfuric acid solution.

The diagram shows two bottles of liquid oven cleaner. 

The oven cleaners contain sodium hydroxide solution. Plan an investigation to show which oven cleaner contains the highest concentration of sodium hydroxide. 

A student investigated the reaction between aqueous sodium hydroxide and acid K.
Two experiments were carried out. 

Experiment 1

Using a measuring cylinder, 25 cm³ of acid K was poured into a conical flask.
Phenolphthalein indicator was added to the flask. A burette was filled with aqueous sodium hydroxide to the 0.0 cm³ mark. Aqueous sodium hydroxide was added from the burette to the flask and the mixture shaken until the solution showed a permanent colour change.
The final volume was measured. Use the burette diagram to record the final volume in the table and complete the table.

Experiment 2
The solution was poured away and the conical flask rinsed.
Using a measuring cylinder, 50 cm³ of acid K was poured into the conical flask. 0.3 g of powdered calcium carbonate was added to the flask and the flask shaken until no further reaction was observed.
Phenolphthalein was added to the mixture in the flask.
A burette was filled with the same aqueous sodium hydroxide and the initial volume measured. Aqueous sodium hydroxide was added from the burette to the flask and the mixture shaken until the solution showed a permanent colour change.
Use the burette diagrams to record the initial and final volumes in the table and complete the table.

What type of chemical reaction occurred when acid K reacted with sodium hydroxide?

If Experiment 1 were repeated using 50 cm³ of acid K, what volume of sodium hydroxide would be required to change the colour of the indicator?

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What would be the effect on the results if the solutions of acid K were warmed before adding the sodium hydroxide? Give a reason for your answer.

Separate: Chemistry Only

Suggest the advantage, if any, of 

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