1.541 ± 0.001 g of hydrated oxalic acid crystals were dissolved in distilled water. The solution was placed in a 250.0 ± 0.5 cm3 volumetric flask and the total volume made up to the mark with distilled water. After thoroughly mixing the contents, 25.00 ± 0.04 cm3 of this solution was pipetted into a conical flask. This required 24.90 ± 0.08 cm3 of 0.100 ± 0.001 mol dm3 sodium hydroxide solution to be neutralized completely.
The equation for the reaction is:
(COOH)2(aq) + 2NaOH(aq) → (COONa)2(aq) + 2H2O(l)
(a) Calculate the percentage uncertainty associated with:
(i) the mass of the oxalic acid.
(ii) the volume of the solution in the volumetric flask.
(iii) the volume in the pipette.
(iv) the molarity of the sodium hydroxide solution.
(v) the volume of sodium hydroxide solution used.
(b) Calculate the total percentage uncertainty for this experiment.
(c) Calculate the molar mass of the oxalic acid obtained from these experimental results to the correct number of significant figures and state the uncertainty.
(d) The correct literature value for the molar mass of the acid is 126.06 g mol-1. Calculate the percentage error.
(e) State any other assumptions which may have affected the accuracy of the result.
Answers
Answer:
1.541 ± 0.001 g of hydrated oxalic acid crystals were dissolved in distilled water. The solution was placed in a 250.0 ± 0.5 cm3 volumetric flask and the total volume made up to the mark with distilled water. After thoroughly mixing the contents, 25.00 ± 0.04 cm3 of this solution was pipetted into a conical flask. This required 24.90 ± 0.08 cm3 of 0.100 ± 0.001 mol dm3 sodium hydroxide solution to be neutralized completely.
The equation for the reaction is:
(COOH)2(aq) + 2NaOH(aq) → (COONa)2(aq) + 2H2O(l)
(a) Calculate the percentage uncertainty associated with:
(i) the mass of the oxalic acid.
(ii) the volume of the solution in the volumetric flask.
(iii) the volume in the pipette.
(iv) the molarity of the sodium hydroxide solution.
(v) the volume of sodium hydroxide solution used.
(b) Calculate the total percentage uncertainty for this experiment.
(c) Calculate the molar mass of the oxalic acid obtained from these experimental results to the correct number of significant figures and state the uncertainty.
(d) The correct literature value for the molar mass of the acid is 126.06 g mol-1. Calculate the percentage error.
(e) State any other assumptions which may have affected the accuracy of the result.