The concentration of a potassium hydroxide solution can be found by titration using a standard solution of ethanedioic acid dihydrate.
Calculate the mass, in g, of solid ethanedioic acid dihydrate (Mr=126.0M_r = 126.0Mr=126.0) needed to prepare 250 cm3250\text{ cm}^3250 cm3 of 0.0600 mol dm−30.0600\text{ mol dm}^{-3}0.0600 mol dm−3 ethanedioic acid solution.
The mass of ethanedioic acid dihydrate from part (a) is dissolved in a beaker containing 100 cm3100\text{ cm}^3100 cm3 of distilled water. Describe how this solution is used to make 250 cm3250\text{ cm}^3250 cm3 of the 0.0600 mol dm−30.0600\text{ mol dm}^{-3}0.0600 mol dm−3 ethanedioic acid solution.
Before the first titration, the 25.0 cm325.0\text{ cm}^325.0 cm3 pipette is rinsed with a small volume of the 0.0600 mol dm−30.0600\text{ mol dm}^{-3}0.0600 mol dm−3 ethanedioic acid solution. State why it is good practice to rinse the pipette in this way.
Potassium hydroxide is added to the burette using a funnel. State why it is good practice to remove the funnel from the burette before the titration.
In a different experiment, 1.42 g1.42\text{ g}1.42 g of solid ethanedioic acid dihydrate is used to make 250 cm3250\text{ cm}^3250 cm3 of standard ethanedioic acid solution. 25.0 cm325.0\text{ cm}^325.0 cm3 of this ethanedioic acid solution reacts with exactly 22.85 cm322.85\text{ cm}^322.85 cm3 of potassium hydroxide solution. The equation for the reaction is:
H2C2O4(aq)+2KOH(aq)→K2C2O4(aq)+2H2O(l) \text{H}_2\text{C}_2\text{O}_4(\text{aq}) + 2\text{KOH}(\text{aq}) \rightarrow \text{K}_2\text{C}_2\text{O}_4(\text{aq}) + 2\text{H}_2\text{O}(\text{l}) H2C2O4(aq)+2KOH(aq)→K2C2O4(aq)+2H2O(l)Calculate the concentration of the potassium hydroxide solution. Give your answer to 3 significant figures.
The uncertainty in the 25.0 cm325.0\text{ cm}^325.0 cm3 of solution from the pipette is ±0.06 cm3\pm0.06\text{ cm}^3±0.06 cm3. The total uncertainty in the 22.85 cm322.85\text{ cm}^322.85 cm3 of solution from the burette is ±0.10 cm3\pm0.10\text{ cm}^3±0.10 cm3. Calculate the total percentage error in using the pipette and burette. Give your answer to 2 significant figures.
79 exam-style questions on AQA A Level Chemistry Amount of substance, covering Relative atomic mass and relative molecular mass, The mole and the Avogadro constant, The ideal gas equation, Empirical and molecular formula, and Balanced equations and associated calculations. Each one has a worked solution and a mark scheme showing where the marks go.