A quality-control chemist checks a batch of rust-removal solution containing phosphoric acid. The analysis certificate records the phosphoric acid content in mol dm−3\mathrm{mol\,dm^{-3}}moldm−3.
A 20.0 cm320.0\,\mathrm{cm^{3}}20.0cm3 sample of the rust-removal solution is exactly neutralised by 24.60 cm324.60\,\mathrm{cm^{3}}24.60cm3 of 0.150 mol dm−30.150\,\mathrm{mol\,dm^{-3}}0.150moldm−3 potassium hydroxide solution.
H3PO4(aq)+3KOH(aq)→K3PO4(aq)+3H2O(l)\mathrm{H_{3}PO_{4}(aq) + 3KOH(aq) \rightarrow K_{3}PO_{4}(aq) + 3H_{2}O(l)}H3PO4(aq)+3KOH(aq)→K3PO4(aq)+3H2O(l)
Use the titration result to calculate the value that should be entered on the analysis certificate.
151 exam-style questions on Edexcel GCSE Chemistry 6.2 Quantitative analysis, covering 6.2.1 Concentration in mol dm⁻³ and titration calculations, 6.2.2 Percentage yield and why actual yield falls short, 6.2.3 Atom economy of a reaction, 6.2.4 Choosing a reaction pathway, and 6.2.5 Molar volume of gases and Avogadro's law. Each one has a worked solution and a mark scheme showing where the marks go.