Acids donate $$\(\mathrm{H}^{+}\)$$in aqueous solution. The number of moles of $$\(\mathrm{H}^{+}\)$$donated per mole of acid is the proticity of the acid. For example, sulfuric acid is diprotic as it donates two moles of $$\(\mathrm{H}^{+}\)$$per mole of acid. In this experiment you will carry out a titration to determine the proticity of citric acid, $$\(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\)$$. FB 1 is aqueous citric acid containing $$\(7.50 \mathrm{~g} \mathrm{dm}^{-3} \mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}\)$$. FB 2 is aqueous sodium hydroxide containing $$\(4.50 \mathrm{~g} \mathrm{dm}^{-3} \mathrm{NaOH}\)$$. FB 3 is thymolphthalein indicator. A student uses a pipette labelled $$\(25.0 \pm 0.06 \mathrm{~cm}^{3}\)$$ to measure FB 1 . The student suggests that it is more accurate to measure the volume of $$\(\mathbf{F B} \mathbf{1}\)$$ with a burette instead of the pipette. State whether the student's suggestion is correct. Explain your answer. .

Chemistry
IGCSE&ALevel
CAIE
Exam No:9701_s25_qp_32 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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