Acid–base titrations：練習題

When performing a titration, a student adds phenolphthalein indicator to the sodium hydroxide solution in the conical flask. The flask is placed on a white tile.
What is the purpose of using the white tile during the titration?

In a titration, \(25.0\ cm^3\) of \(0.10\ mol/dm^3\) \(NaOH\) reacts with \(25.0\ cm^3\) of \(0.10\ mol/dm^3\) \(HCl\). What is the total number of moles of water produced in this reaction?

A student performed four titration trials to determine the concentration of an acid. The results are shown in the table below.
Which trials are concordant and what is the mean titre that should be used for calculations?

Which piece of apparatus is specifically designed to deliver an accurately measured, fixed volume of \(25.0\ cm^3\) of a solution into a conical flask during an acid–base titration?

A student prepares a burette for a titration by rinsing it with distilled water. They then immediately fill the burette with the standard \(0.100\ mol/dm^3\) hydrochloric acid solution without rinsing it with the acid first.
How does this procedural error affect the calculated concentration of the unknown alkali?

Define the term end-point in the context of an acid–base titration using an indicator.

Explain why the first titration performed in a series is usually referred to as a rough titration.

In a titration, \(20.0\text{ cm}^3\) of sulfuric acid, \(H_2SO_4\), is neutralised by \(25.0\text{ cm}^3\) of \(0.20\text{ mol/dm}^3\) sodium hydroxide, \(NaOH\). The equation is:
\(H_2SO_4 + 2NaOH \rightarrow Na_2SO_4 + 2H_2O\)
Calculate the concentration of the acid in \(mol/dm^3\).

A student performs two separate titrations using \(25.0\ cm^3\) of the same \(0.100\ mol/dm^3\) sodium hydroxide solution each time.
In Experiment 1, they use \(0.100\ mol/dm^3\) hydrochloric acid, \(HCl\).
In Experiment 2, they use \(0.100\ mol/dm^3\) sulfuric acid, \(H_2SO_4\).
(a) Predict the volume of acid needed for Experiment 1 and Experiment 2.
(b) Explain the difference in the volumes calculated in part (a) by referring to the basicity of the two acids.
(c) Write the ionic equation for the neutralisation reaction that occurs in both experiments, including state symbols.

A student recorded the following results from a titration between hydrochloric acid and \(25.0\ cm^3\) of sodium carbonate solution.

Titration 1 (Rough): \(23.50\ cm^3\)
Titration 2: \(22.10\ cm^3\)
Titration 3: \(22.20\ cm^3\)
Titration 4: \(22.15\ cm^3\)

(a) Identify the concordant titres from the results above.
(b) Calculate the average titre value to be used for further calculations.
(c) Explain why the student performs a 'rough' titration first.
(d) Suggest one reason why the first titration value is usually higher than the subsequent ones.