The molar concentration of Cu 2 + should be determined. Concept introduction: Calibration of instrumental methods: The purpose of calibration which is required by all types of analytical methods is quantitation. It is defined as a process in which the measured analytical signal and the concentration of analyte are related to each other. The three most common methods to calibrate are: Calibration curve. Standard addition method. Internal standard method. In case of standard addition method, standards are added to the aliquots of sample, keeping the matrix components same. On each solution, instrumental measurements are made to obtain instrument response ( S ). The relation between the instrument response and concentration if they are proportional is, S = k V S C S V t + k V x C x V t Where, V x represents the volume of sample. V S represents the volume of standard. V t represents the total volume of flask. C s represents the concentration of standard. C x represents the concentration of analyte in aliquot. k represents the proportionality constant.

Question

A solution of Ba(OH)2 was standardized against0.1215 g of primary-standard-grade benzoic acid, C6H5COOH (122.12 g/mol). An end point was observedafter addition of 43.25 mL of base. (a) Calculate the molar concentration of the base. (b) Calculate the standard deviation of the molarconcentration if the standard deviation for themass measurement was ±0.3 mg and that for thevolume measurement was ±0.02 mL. (c) Assuming an error of ±0.3 mg in the mass measurement,calculate the absolute and relative systematicerror in the molar concentration.

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Chapter 1, Problem 1.9QAP

Interpretation Introduction

Interpretation:

The molar concentration of Cu2+ should be determined.

Concept introduction:

Calibration of instrumental methods: The purpose of calibration which is required by all types of analytical methods is quantitation. It is defined as a process in which the measured analytical signal and the concentration of analyte are related to each other. The three most common methods to calibrate are:

Calibration curve.

Standard addition method.

Internal standard method.

In case of standard addition method, standards are added to the aliquots of sample, keeping the matrix components same. On each solution, instrumental measurements are made to obtain instrument response ( S ).

The relation between the instrument response and concentration if they are proportional is,

S=kVSCSVt+kVxCxVt

Where,

Vx represents the volume of sample.

VS represents the volume of standard.

Vt represents the total volume of flask.

Cs represents the concentration of standard.

Cx represents the concentration of analyte in aliquot.

k represents the proportionality constant.

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