A method for the analysis of Ca^2+ in water suffers from an interference in the presence of Zn^2

step 1 For a galvanic cell in which zinc oxidizes into ZN2 plus ion releasing two electrons where e -ox

A method for the analysis of Ca^2+ in water suffers from an...

A method for the analysis of $\mathrm{Ca}^{2+}$ in water suffers from an interference in the presence of $\mathrm{Zn}^{2+}$. When the concentration of $\mathrm{Ca}^{2+}$ is 50 times greater than that of $\mathrm{Zn}^{2+}$, an analysis for $\mathrm{Ca}^{2+}$ gives a relative error of $-2.0 \%$. What is the value of the selectivity coefficient for this method?

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Key Concepts

Relative Error

Relative error is the measure of the discrepancy between an observed value and the true or accepted value, expressed as a percentage. In analytical chemistry, it quantifies how much the measured result deviates from the actual concentration, allowing one to assess the accuracy of an analytical method in the presence of systematic errors or interferences.

Selectivity Coefficient

The selectivity coefficient is a parameter that quantifies the response of an analytical sensor or method to an interfering ion relative to the analyte of interest. It is used to evaluate the degree to which the presence of another ion affects the measurement, and its value helps in correcting or compensating for such interference in quantitative analyses.

Interference in Analytical Methods

Interference in analytical methods occurs when an additional substance alters the measurement outcome of the target analyte. This effect can lead to errors, such as a negative relative error, by causing the analytical method to under- or over-estimate the concentration of the analyte. Understanding interference is crucial for ensuring accurate and reliable analytical measurements.

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