# (a) Interpretation: An equation that relates the desired quantity, mass S 2 - (ng), to the chloridometer readout in mass Cl- (ng) should be derived. Concept introduction: Chloridometer is used in chlorine determination. The number of moles of chloride in an unknown solution can be determined by the following equation. ( n C l − ) u = t u t s × ( n C l − ) s ( n C l − ) u = number of moles of chloride in the unknown sample ( n C l − ) s = number of moles of chloride in the standard sample t u = time required to titrate the unknown chloride solution t s = time required to titrate the standard chloride solution

### Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

### Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

#### Solutions

Chapter 24, Problem 24.13QAP
Interpretation Introduction

## (a)Interpretation:An equation that relates the desired quantity, mass S2- (ng), to the chloridometer readout in mass Cl- (ng) should be derived.Concept introduction:Chloridometer is used in chlorine determination. The number of moles of chloride in an unknown solution can be determined by the following equation.(nCl−)u=tuts×(nCl−)s(nCl−)u = number of moles of chloride in the unknown sample(nCl−)s = number of moles of chloride in the standard sampletu = time required to titrate the unknown chloride solutionts = time required to titrate the standard chloride solution

Interpretation Introduction

### (b)Interpretation:Total charge in coulombs required to generate the Ag+ needed to precipitate the sulfide in the standard should be determined.Concept introduction:The number of moles can be calculated from mass and molar mass as follows:n=mMHere, m is mass and M is molar mass.Charge of 1 mole of electron transferred = 96485 C

Interpretation Introduction

### (c)Interpretation:Each of the chloride results should be converted to mass S2- (ng)Concept introduction:The number of moles can be calculated from mass and molar mass as follows:n=mMHere, m is mass and M is molar mass.

Interpretation Introduction

### (d)Interpretation:The average mass of S2-, standard deviation, and the % RSD of each standard should be determined.Concept introduction:The mean value for mass can be calculated as follows:X¯=∑XiNThe standard deviation can be calculated as follows:s=∑(xi−x¯)N−1The value of % RSD can be calculated as follows:%RSD=sx¯×100Here, s is a standard deviation and x¯ is mean value.

Interpretation Introduction

### (e)Interpretation:A plot of the average mass of S2- determined (ng) versus the actual mass (ng) should be prepared. Slope, intercept and standard error and R2 value should be determined.Concept introduction:In the plot,X-axis = actual mass of S2-Y-axis = determined mass of S2-

Interpretation Introduction

### (f)Interpretation:The detection limit (ng) and in parts per million using a k factor of 2 should be determined.Concept introduction:The minimum distinguishable analytical signal can be calculated as follows:Sm=S¯bl+ksblHere,Sm - the minimum distinguishable analytical signalS¯bl - mean blank signalk − constantsbl - the standard deviation of the blank signals.

Interpretation Introduction

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