Hydrogen peroxide, $$\(\mathrm{H}_{2} \mathrm{O}_{2}\)$$, reacts rapidly with acidified potassium manganate(VII), $$\(\mathrm{KMnO}_{4}\)$$. $$\[ 5 \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq})+2 \mathrm{MnO}_{4}^{-}(\mathrm{aq})+6 \mathrm{H}^{+}(\mathrm{aq}) \rightarrow 5 \mathrm{O}_{2}(\mathrm{~g})+8 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+2 \mathrm{Mn}^{2+}(\mathrm{aq}) \]$$ You will determine the concentration of a solution of hydrogen peroxide. You will first dilute the solution and then carry out a titration with acidified potassium manganate(VII). FA 1 is aqueous hydrogen peroxide, $$\(\mathrm{H}_{2} \mathrm{O}_{2}\)$$. FA 2 is $$\(0.0300 \mathrm{~mol} \mathrm{dm}^{-3}\)$$ potassium manganate(VII), $$\(\mathrm{KMnO}_{4}\)$$. FA 3 is $$\(1.0 \mathrm{~mol} \mathrm{dm}^{-3}\)$$ sulfuric acid, $$\(\mathrm{H}_{2} \mathrm{SO}_{4}\)$$. A student suggests that the experiment would be more accurate if a $$\(10 \mathrm{~cm}^{3}\)$$ pipette is used to measure FA 3 in place of the measuring cylinder. State whether the student's suggestion is correct. Explain your answer. Include a calculation as part of your explanation. . . .

Chemistry
IGCSE&ALevel
CAIE
Exam No:9701_s25_qp_33 Year:2025 Question No:1(d)

Answer:



Knowledge points:

2.4.1.1 reacting masses (from formulae and equations) including percentage yield calculations
2.4.1.2 volumes of gases (e.g. in the burning of hydrocarbons)
2.4.1.3 volumes and concentrations of solutions
2.4.1.4 limiting reagent and excess reagent (When performing calculations, candidates’ answers should reflect the number of significant figures given or asked for in the question. When rounding up or down, candidates should ensure that significant figures are neither lost unnecessarily nor used beyond what is justified (see also Mathematical requirements section).) deduce stoichiometric relationships from calculations such as those in 2.4.1 (1)–(4)

Solution:

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