30. Solving a chemistry problem

30. Solving a chemistry problem

10. To assess the reproducibility and correctness of the analysis procedure, a sample of the DL-methionine preparation (extra-pure substance) was carefully analyzed by non-aqueous potentiometric titration and the W content (mass fraction) of the main substance in five parallel determinations was found to be equal, %. 99.900; 99.910; 99.910;99.920; 99,930. The true content of the main substance in the preparation is Mu=99.900%. Describe the method of analysis in terms of reproducibility (by calculating the confidence interval) W±ΔW and the relative error ε of the average result of the analysis) at a confidence level Р=0.95. Answer W±ΔW=(99.914±0.013)% ε=0.01%. The true value of 99.900 is less than the lower limit (99.901) of the confidence interval. There is an insignificant systematic error b = 0.01%, not exceeding the random error.

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