Qualitative Data
- When amidosulphuric acid was diluted with distilled water, the beaker feels cold.
- When the phenolphthalein indicator was dropped into the solution, the solution color does not change and remains clear.
- When the diluted amidosulphuric acid was titrated with the sodium hydroxide solution, the color of the solution turns to pale pink and it is called an endpoint. Mass of amidosulphuric acid powder = 2. 5050 g ± 0. 0001 g
Calculation
The average volume of sodium hydroxide solution used =First reading+Second reading+Third reading
3 24. 7 + 29. 8 + 27. 0 3 = 27. 2 cm3 = 27. 2 cm3 ± 0. 1 cm3
Chemical equation: H3NSO3 + NaOH > NaH2NSO3 + H2O No of mole of sodium hydroxide, n=Molarity of solution?
Volume of solution 1000 = 0. 002720 mol 1 mole of NaOH reacts with 1 mole of H3NSO3 So, 0. 002720 mol of NaOH reacts with 0. 002720 mol of H3NSO3
Volume of solution = 0. 0109 mol dm-3
The relative molecular mass of 250. 00 cm3 amidosulphuric acid, RMM= Mass of compound
No of a mole of the compound 10 = 2. 50500. 002720 = 92. 20 g mol-1
Error Analysis
- Burette = 0. 127. 2? 100% = 0. 3676 %
- Pipette = 0. 0325. 00? 100% = ± 0. 1200 %
- Volumetric flask = 0. 15250. 00? 100% 0. 06000 %
- Analytical balance = 0. 00012. 5050? 100% = 0. 004000 %
Total percentage error = 0. 3676% + 0. 1200% + 0. 06000% + 0. 004000% = 0. 5516 %
Absolute error = ±0. 5086 g mol-1
Conclusion and Evaluation
From the experiment, the relative molecular mass of amidosulphuric acid obtain is 92. 20 g mol-1 ± 0. 5086 g mol-1. The total percentage error from the instrument is 0. 5516%. The experimental value obtain is smaller than the theoretical value of the acid which is 97. 1 g mol-1. This different is most likely from systematic errors and also random errors during the experiment. The errors are may come from
- There are some of the powdered amidosulphuric acids left at the weighing bottle.
- There is a parallax error when the observer taking the reading of sodium hydroxide solution in the burette.
- Overshot happen during the titration which affects the amount of sodium hydroxide used to neutralize the amidosulphuric acid.