Chemistry 5070 · O Level · Experimental design

Experimental design — practice question

A student determines the amount of iron(II) ions in a solution by titration. The student: • uses a volumetric pipette to transfer $25.0\,\text{cm}^3$ of aqueous iron(II) sulfate into a conical flask • adds about $20\,\text{cm}^3$ of dilute sulfuric acid to the flask • slowly runs aqueous potassium manganate(VII) into the conical flask until the solution just becomes pink • carries out the titration again several times.
(a(i))[1]

Fig. 1.1 shows the apparatus the student uses to measure the volume of dilute sulfuric acid. What is the name of the apparatus shown in Fig. 1.1?

(a(ii))[1]

Explain why the student does not need to use a volumetric pipette to measure the volume of dilute sulfuric acid.

(a(iii))[1]

Describe how the student uses the volumetric pipette to measure $25.0\,\text{cm}^3$ of aqueous iron(II) sulfate safely.

(b)[1]

Name the apparatus the student uses to add the aqueous potassium manganate(VII) to the flask.

(c)[1]

State why the student does not need to add an indicator to this titration.

(d)[1]

Explain how the student knows when they have done enough titrations.

Worked solution & mark scheme

This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: a measuring cylinder

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