A student finds the concentration of sulfuric acid in car battery acid. She dilutes 5.0 cm3\mathrm{cm^{3}}cm3 of battery acid with distilled water to make 250 cm3\mathrm{cm^{3}}cm3 of solution. She titrates 25.0 cm3\mathrm{cm^{3}}cm3 portions of the diluted acid with 0.200 mol dm−3\mathrm{mol\,dm^{-3}}moldm−3 sodium hydroxide solution.
H2SO4(aq)+2NaOH(aq)→Na2SO4(aq)+2H2O(l)\mathrm{H_{2}SO_{4}(aq)} + \mathrm{2NaOH(aq)} \rightarrow \mathrm{Na_{2}SO_{4}(aq)} + \mathrm{2H_{2}O(l)}H2SO4(aq)+2NaOH(aq)→Na2SO4(aq)+2H2O(l)
The table shows her titres.
| Titration | rough | 1 | 2 | 3 |
|---|---|---|---|---|
| Titre / cm3\mathrm{cm^{3}}cm3 | 25.50 | 25.05 | 24.60 | 24.95 |
Determine the mean titre that the student should use.
Calculate the concentration of sulfuric acid in the diluted solution, in mol dm−3\mathrm{mol\,dm^{-3}}moldm−3.
Calculate the concentration of sulfuric acid in the undiluted battery acid in mol dm−3\mathrm{mol\,dm^{-3}}moldm−3, and convert it to g dm−3\mathrm{g\,dm^{-3}}gdm−3. Relative formula mass: H2SO4=98\mathrm{H_{2}SO_{4}} = 98H2SO4=98
The student rinses the burette with the sodium hydroxide solution, not with water, before filling it. Explain why rinsing with water would give an incorrect value for the concentration of the acid.
51 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.