page_content stringlengths 12 2.63M | metadata unknown |
|---|---|
breakthrough volume (*p. 196*) composite sample (*p. 186*) coning and quartering (*p. 199*) convenience sampling (*p. 185*) dialysis (*p. 206*) distribution ratio (*p. 216*) extraction (*p. 212*) grab sample (*p. 185*) gross sample (*p. 193*) in situ sampling (*p. 186*)
judgmental sampling (*p. 184*) laboratory sampl... | {
"Header 1": "**7I KEY TERMS**",
"token_count": 304,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
An analysis requires a sample, and how we acquire the sample is critical. To be useful, the samples we collect must accurately represent their target population. Just as important, our sampling plan must provide a sufficient number of samples of appropriate size so that the variance due to sampling does not limit the p... | {
"Header 1": "**7J SUMMARY**",
"token_count": 362,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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*The following set of experiments introduce students to the important effect of sampling on the quality of analytical results. Each experiment is annotated with a brief description of the principles that it emphasizes.*
Bauer, C. F. "Sampling Error Lecture Demonstration," *J. Chem. Edu... | {
"Header 1": "**7K** *Suggested* **EXPERIMENTS**",
"token_count": 1006,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Continued from page 225
The following experiments introduce students to the importance of sample preparation and methods for extracting analytes from their matrix. Each experiment includes a brief description of the sample and analyte, as well as the method of analysis used to measure the analyte's concentration.
D... | {
"Header 1": "Experiments",
"token_count": 1991,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Assume that the particles are spherical with a radius of *r* and a density of *d.*
- **9.** The sampling constant for the radioisotope 24Na in a sample of homogenized human liver has been reported as approximately 35 g.25 (a) What is the expected relative standard deviation for sampling if 1.0-g samples are analyzed? (... | {
"Header 1": "Experiments",
"token_count": 1785,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
#### **Parts per Million Hg Following Microwave Digestion**
| 1<br>7.12<br>7.66<br>7.17<br>2<br>16.1<br>15.7<br>15.6 | |
|--------------------------------------------------------|--|
| | |
| | |
| 3<br>4... | {
"Header 1": "Experiments",
"token_count": 1983,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
What is the expected relative error if the selectivity coefficient, *K*HA,HB, is 0.500 and the initial ratio of HB/HA was 10.0?
- **31.** The relevant equilibria for the extraction of I2 from an aqueous solution of KI into an organic phase are shown in the following diagram.
(a) Will ... | {
"Header 1": "Experiments",
"token_count": 942,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The following paper provides a general introduction to the terminology used in describing sampling.
Majors, R. E. "Nomenclature for Sampling in Analytical Chemistry." *LC•GC* **1992,** *10,* 500–506.
Further information on the statistics of sampling is covered in the following papers.
Kratochvil, B.; Goewie, C. E... | {
"Header 1": "**7M SUGGESTED READINGS**",
"token_count": 1083,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
- 1. Youden, Y. J. *J. Assoc. Off. Anal. Chem.* **1981,** *50,* 1007–1013.
- 2. Fricke, G. H.; Mischler, P. G.; Staffieri, F. P.; et al. *Anal. Chem.* **1987,** *59,* 1213–1217.
- 3. (a) Cohen, R. D. *J. Chem. Educ.* **1991,** *68,* 902–903; (b) Cohen, R. D. *J. Chem. Educ.* **1992,** *69,* 200–203.
- 4. Keith, L. H. *... | {
"Header 1": "**7N REFERENCES**",
"token_count": 1355,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Before we look more closely at specific gravimetric methods and their applications, let's take a moment to develop a broad survey of **gravimetry**. Later, as you read through the sections of this chapter discussing different gravimetric methods, this survey will help you focus on their similarities. It is usually easi... | {
"Header 1": "8A Overview of Gravimetry",
"token_count": 1108,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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In the previous section we used four examples to illustrate the different ways that mass can serve as an analytical signal. These examples also illustrate the four gravimetric methods of analysis. When the signal is the mass of a precipitate, we call the method **precipitation gravimetry.** The indirect determination o... | {
"Header 1": "**8A.2 Types of Gravimetric Methods**",
"token_count": 296,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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An accurate gravimetric analysis requires that the mass of analyte present in a sample be proportional to the mass or change in mass serving as the analytical signal. For all gravimetric methods this proportionality involves a conservation of mass. For gravimetric methods involving a chemical reaction, the analyte shou... | {
"Header 1": "**8A.3 Conservation of Mass**",
"token_count": 384,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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A precipitation gravimetric analysis must have several important attributes. First, the precipitate must be of low solubility, high purity, and of known composition if its mass is to accurately reflect the analyte's mass. Second, the precipitate must be in a form that is easy to separate from the reaction mixture. The ... | {
"Header 1": "**8B.1 Theory and Practice**",
"token_count": 2040,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Silver and chloride ions are not shown to scale.
**Avoiding Impurities** Precipitation gravimetry is based on a known stoichiometry between the analyte's mass and the mass of a precipitate. It follows, therefore, that the precipitate must be free from impurities. Since precipitation typically occurs in a solution ric... | {
"Header 1": "**8B.1 Theory and Practice**",
"token_count": 2026,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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For example, a mixture containing Ca2+ and Mg2+ can be analyzed for both cations by first isolating a mixed precipitate of CaCO3 and MgCO3. After weighing, the mixed precipitate is heated, converting it to a mixture of CaO and MgO. Thus
Grams of mixed precipitate 1 = grams CaCO3 + grams MgCO3
Grams of mixed precipi... | {
"Header 1": "**8B.1 Theory and Practice**",
"token_count": 2020,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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**Filtering the Precipitate** After precipitation and digestion are complete, the precipitate is separated from solution by filtration using either filter paper or a filtering crucible. The most common filtering medium is cellulose-based filter paper, which is classified according to its filtering speed, its size, an... | {
"Header 1": "**8B.1 Theory and Practice**",
"token_count": 2033,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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#### Determination of Mg2+ in Water and Wastewater7
**Description of Method.** Magnesium is precipitated as MgNH<sub>4</sub>PO<sub>4</sub> • 6H<sub>2</sub>O using (NH<sub>4</sub>)<sub>2</sub>HPO<sub>4</sub> as the precipitant. The precipitate's solubility in neutral solutions (0.0065 g/100 mL in pure water at 10 °C) ... | {
"Header 1": "Method 8.1",
"token_count": 1711,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Many inorganic anions can be determined using the same reactions by reversing the analyte
| Table 8.1 | Selected Gravimetric Method for Inorganic Cations<br>Based on Precipitation | | | |
|-----------|-----------------------------------------------------------------------------... | {
"Header 1": "Method 8.1",
"token_count": 996,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Precipitation is carried out in an
| Table 8.3 | Reactions for the Homogeneous<br>Preparation of Selected |
|-----------|----------------------------------------------------------|
| | Inorganic Precipitants |
| Precipitant | Reaction ... | {
"Header 1": "Method 8.1",
"token_count": 1885,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Applying a conservation of mass to Fe, we write
$$3 \times \text{moles Fe}_3O_4 = 2 \times \text{moles Fe}_2O_3$$
Using formula weights, FW, to convert from moles to grams in the preceding equation leaves us with
$$\frac{3 \times g \operatorname{Fe}_{3} \operatorname{O}_{4}}{\operatorname{FW} \operatorname{Fe}_{3... | {
"Header 1": "Method 8.1",
"token_count": 456,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
A 0.6113-g sample of Dow metal, containing aluminum, magnesium, and other metals, was dissolved and treated to prevent interferences by the other metals. The aluminum and magnesium were precipitated with 8-hydroxyquinoline. After filtering and drying, the mixture of Al(C<sub>9</sub>H<sub>6</sub>NO)<sub>3</sub> and Mg(C... | {
"Header 1": "EXAMPLE 8.2",
"token_count": 2017,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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A solution containing 50 mL of 3% w/v mercury(II) chloride, 20 mL of 10% w/v sodium acetate and 5 mL of glacial acetic acid was then prepared. The solution containing the phosphite was added dropwise to the second solution, oxidizing PO<sub>3</sub><sup>3-</sup> to PO<sub>4</sub><sup>3-</sup> and precipitating Hg<sub>2<... | {
"Header 1": "EXAMPLE 8.2",
"token_count": 1853,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
A second approach to gravimetry is to thermally or chemically decompose a solid sample. The volatile products of the decomposition reaction may be trapped and weighed to provide quantitative information. Alternatively, the residue remaining when decomposition is complete may be weighed. In **thermogravimetry**, which i... | {
"Header 1": "**8C** Volatilization Gravimetry",
"token_count": 1500,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
#### Determination of Si in Ores and Alloys9
**Description of Method.** Silicon is determined by dissolving the sample in acid. Dehydration of the resulting solution precipitates silicon as $SiO_2$ . Because a variety of other insoluble oxides also form, the precipitate's mass does not provide a direct measure of th... | {
"Header 1": "Method 8.2",
"token_count": 978,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Unlike precipitation gravimetry, which is rarely used as a standard method of analysis, gravimetric methods based on volatilization reactions continue to play an important role in chemical analysis. Several important examples are discussed in the following sections.
**Inorganic Analysis** Determining the inorganic as... | {
"Header 1": "**8C.2 Quantitative Applications**",
"token_count": 1929,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
A sample of slag from a blast furnace is analyzed for SiO<sub>2</sub> by decomposing a 0.5003-g sample with HCl, leaving a residue with a mass of 0.1414 g. After treating with HF and H<sub>2</sub>SO<sub>4</sub> and evaporating the volatile SiF<sub>4</sub>, a residue with a mass of 0.0183 g remains. Determine the %w/w S... | {
"Header 1": "EXAMPLE 8.6",
"token_count": 1088,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Two approaches have been used to separate the analyte from its matrix in particulate gravimetry. The most common approach is filtration, in which solid particulates are separated from their gas, liquid, or solid matrix. A second approach uses a liquid-phase or solid-phase extraction.
**Filtration** Liquid samples are... | {
"Header 1": "**8D.1 Theory and Practice**",
"token_count": 1014,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Particulate gravimetry is commonly encountered in the environmental analysis of water, air, and soil samples. The analysis for suspended solids in water samples, for example, is accomplished by filtering an appropriate volume of a well-mixed sample through a glass fiber filter and drying the filter to constant weight a... | {
"Header 1": "**8D.2 Quantitative Applications**",
"token_count": 585,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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The scale of operation and detection limit for particulate gravimetry can be extended beyond that of other gravimetric methods by increasing the size of the sample taken for analysis. This is usually impossible for other gravimetric methods because of the difficulty of manipulating a larger sample through the individua... | {
"Header 1": "**8D.3 Evaluating Particulate Gravimetry**",
"token_count": 236,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
adsorbate (*p. 239*) coagulation (*p. 242*) digestion (*p. 239*) electrogravimetry (*p. 234*) gravimetry (*p. 233*) homogeneous precipitation (*p. 241*) inclusion (*p. 238*) occlusion (*p. 239*) particulate gravimetry (*p. 234*) peptization (*p. 245*) precipitant (*p. 235*) precipitation gravimetry (*p. 234*) relative ... | {
"Header 1": "**8E KEY TERMS**",
"token_count": 205,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
In a gravimetric analysis a measurement of mass or change in mass provides quantitative information about the amount of analyte in a sample. The most common form of gravimetry uses a precipitation reaction to generate a product whose mass is proportional to the analyte. In many cases the precipitate includes the analyt... | {
"Header 1": "**8E KEY TERMS**",
"Header 3": "**8F SUMMARY**",
"token_count": 233,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
A number of gravimetric methods, such as the determination of Cl<sup>-</sup> in a soluble salt, have been part of the "standard" repertoire of experiments for introductory courses in analytical chemistry. Listed here are additional experiments that may be used to provide practical examp... | {
"Header 1": "Suggested EXPERIMENTS",
"token_count": 935,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
- **1.** Starting with the equilibrium constant expressions for reactions 8.1, and 8.3–8.5, verify that equation 8.7 is correct.
- **2.** Equation 8.7 shows how the solubility of AgCl varies as a function of the equilibrium concentration of Cl<sup>-</sup>. Derive a similar equation to describe the solubility of AgCl as... | {
"Header 1": "Suggested EXPERIMENTS",
"Header 3": "**8H PROBLEMS**",
"token_count": 2001,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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After boiling to remove the oxides of nitrogen, the solution is diluted to 200 mL, brought to boiling, and Fe(OH)<sub>3</sub> is precipitated by slowly adding 1:1 NH<sub>3</sub> until the odor of NH<sub>3</sub> is detected. The solution is boiled for an additional minute, and the precipitate is allowed to settle to the... | {
"Header 1": "Suggested EXPERIMENTS",
"Header 3": "**8H PROBLEMS**",
"token_count": 2041,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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The resulting precipitate was isolated by filtration, rinsed free of impurities, and dried to a constant weight, yielding 863.5 mg of BaSO<sub>4</sub>. What is the %w/w K<sub>2</sub>SO<sub>4</sub> in the sample?
- **18.** The amount of iron and manganese in an alloy can be determined by precipitating the metals with 8-... | {
"Header 1": "Suggested EXPERIMENTS",
"Header 3": "**8H PROBLEMS**",
"token_count": 1815,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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The following data were collected during the analysis of two samples of a polymer resin:
| Polymer A | g crucible | polymer | ash |
|-------------|------------|-------------------------|---------------------|
| replicate 1 | 19.1458 | 21.2287 | 19.7717 ... | {
"Header 1": "Suggested EXPERIMENTS",
"Header 3": "**8H PROBLEMS**",
"token_count": 1993,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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| [thiourea] (M) | ∆f (Hz) |
|----------------|---------|
| 3.00 × 10–7 | 74.6 |
| 5.00 × 10–7 | 120 |
| 7.00 × 10–7 | 159 |
| 9.00 × 10–7 | 205 |
| 15.00 × 10–7 | 327 |
| 25.00 × 10–7 | 543 |
| 35.00 × 10–7 | 789 |
| 50.00 × 10–7 | 1089 |
(a) Characterize this meth... | {
"Header 1": "Suggested EXPERIMENTS",
"Header 3": "**8H PROBLEMS**",
"token_count": 332,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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The following resources provide a general history of gravimetry. Beck, C. M. "Classical Analysis: A Look at the Past, Present, and Future," *Anal. Chem.* **1991,** *63,* 993A–1003A.
Laitinen, H. A.; Ewing, G. W., eds. *A History of Analytical Chemistry.* The Division of Analytical Chemistry of the American Chemical S... | {
"Header 1": "**8I SUGGESTED READINGS**",
"token_count": 382,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
- 1. Valcárcel, M.; Rios, A. *Analyst* **1995,** *120,* 2291–2297.
- 2. (a) Moody, J. R.; Epstein, M. S. *Spectrochim. Acta* **1991,** *46B,* 1571–1575. (b) Epstein, M. S. *Spectrochim. Acta* **1991,** *46B,* 1583–1591.
- 3. Von Weimarn, P. P. *Chem. Revs.* **1925,** *2,* 217.
- 4. Bassett, J.; Denney, R. C.; Jeffery, ... | {
"Header 1": "**8J REFERENCES**",
"token_count": 976,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
**T**itrimetry, in which we measure the volume of a reagent reacting stoichiometrically with the analyte, first appeared as an analytical method in the early eighteenth century. Unlike gravimetry, titrimetry initially did not receive wide acceptance as an analytical technique. Many prominent late-nineteenth century ana... | {
"Header 1": "Titrimetric Methods of Analysis",
"token_count": 408,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
For a titration to be accurate we must add a stoichiometrically equivalent amount of titrant to a solution containing the analyte. We call this stoichiometric mixture the **equivalence point.** Unlike precipitation gravimetry, where the precipitant is added in excess, determining the exact volume of titrant needed to r... | {
"Header 1": "**9A.1 Equivalence Points and End Points**",
"token_count": 303,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Almost any chemical reaction can serve as a titrimetric method provided that three conditions are met. The first condition is that all reactions involving the titrant and analyte must be of known stoichiometry. If this is not the case, then the moles of titrant used in reaching the end point cannot tell us how much ana... | {
"Header 1": "**9A.2 Volume as a Signal\\***",
"token_count": 1067,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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To find the end point we monitor some property of the titration reaction that has a well-defined value at the equivalence point. For example, the equivalence point for a titration of HCl with NaOH occurs at a pH of 7.0. We can find the end point,
#### **back titration**
A titration in which a reagent is added to a ... | {
"Header 1": "**9A.3 Titration Curves**",
"token_count": 837,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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The only essential piece of equipment for an acid–base titration is a means for delivering the titrant to the solution containing the analyte. The most common method for delivering the titrant is a **buret** (Figure 9.4). A buret is a long, narrow tube with graduated markings, and a stopcock for dispensing the titrant.... | {
"Header 1": "**9A.4 The Buret**",
"token_count": 614,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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The earliest **acid–base titrations** involved the determination of the acidity or alkalinity of solutions, and the purity of carbonates and alkaline earth oxides. Before 1800, acid–base titrations were conducted using H2SO4, HCl, and HNO3 as acidic titrants, and K2CO3 and Na2CO3 as basic titrants. End points were dete... | {
"Header 1": "**9B Titrations Based on Acid–Base Reactions**",
"token_count": 486,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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In the overview to this chapter we noted that the experimentally determined end point should coincide with the titration's equivalence point. For an acid–base titration, the equivalence point is characterized by a pH level that is a function of the acid–base strengths and concentrations of the analyte and titrant. The ... | {
"Header 1": "**9B.1 Acid–Base Titration Curves**",
"token_count": 2037,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
$$CH_3COOH(aq) + OH^-(aq) \rightleftharpoons H_2O(\ell) + CH_3COO^-(aq)$$
9.2
Any solution containing comparable amounts of a weak acid, HA, and its conjugate weak base, A<sup>-</sup>, is a buffer. As we learned in Chapter 6, we can calculate the pH of a buffer using the Henderson–Hasselbalch equation.
$$pH = pK_... | {
"Header 1": "**9B.1 Acid–Base Titration Curves**",
"token_count": 2034,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Conversely, the buffer's pH is at its upper limit, pH = p*K*<sup>a</sup> + 1, when the concentration of weak acid is ten times less than that of its conjugate weak base. When titrating a weak acid or weak base, therefore, the buffer region spans a range of volumes from approximately 10% of the equivalence point volume ... | {
"Header 1": "**9B.1 Acid–Base Titration Curves**",
"token_count": 284,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Sketch the titration curve for the titration of 50.0 mL of 0.100 M acetic acid with 0.100 M NaOH. This is the same titration for which we previously calculated the titration curve (Table 9.3 and Figure 9.6).
#### *SOLUTION*
We begin by drawing the axes for the titration curve (Figure 9.7a). We have already shown th... | {
"Header 1": "**EXAMPLE 9.1**",
"token_count": 927,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Earlier we made an important distinction between an end point and an equivalence point. The difference between these two terms is important and deserves repeating. The equivalence point occurs when stoichiometrically equal amounts of analyte and titrant react. For example, if the analyte is a triprotic weak acid, a tit... | {
"Header 1": "**9B.2 Selecting and Evaluating the End Point**",
"token_count": 2027,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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For other indicators both the weak acid and weak base are colored, but one form may be easier to see. In either case, the pH range is skewed toward those pH levels for which the less colored form of the indicator is present in higher concentration.
A list of several common acid–base indicators, along with their p*K*a... | {
"Header 1": "**9B.2 Selecting and Evaluating the End Point**",
"token_count": 1524,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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| Table 9.5 | Data for the Titration of a Weak Acid with |
|-----------|--------------------------------------------|
| | 0.100 M NaOH |
| | 0.100 W NGOTI | | | | |
... | {
"Header 1": "**9B.2 Selecting and Evaluating the End Point**",
"token_count": 1942,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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$$[HA] = \frac{\text{moles HA} - \text{moles OH}^- \text{ added}}{\text{total volume}} = \frac{M_a V_a - M_b V_b}{V_a + V_b}$$
$$[A^-] = \frac{\text{moles OH}^- \text{ added}}{\text{total volume}} = \frac{M_b V_b}{V_a + V_b}$$
Substituting these equations into the $K_a$ expression for HA, and rearranging gives
... | {
"Header 1": "**9B.2 Selecting and Evaluating the End Point**",
"token_count": 1937,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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In an aqueous solution the concentration of $H_3O^+$ when the titration is 90% complete is
$$[H_3O^+] = \frac{M_aV_a - M_bV_b}{V_a + V_b}$$
$$= \frac{(1 \times 10^{-4} \text{ M})(50 \text{ mL}) - (1 \times 10^{-4} \text{ M})(45 \text{ mL})}{50 + 45} = 5.3 \times 10^{-6} \text{ M}$$
corresponding to a pH of 5.3.... | {
"Header 1": "**9B.2 Selecting and Evaluating the End Point**",
"token_count": 1417,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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*Description of the Method.* This quantitative method of analysis for proteins is based on a determination of the %w/w N in the sample. Since different cereal proteins have similar amounts of nitrogen, the experimentally determined %w/w N is multiplied by a factor of 5.7 to give the %w/w protein in the sample (on avera... | {
"Header 1": "**Method 9.1 Determination of Protein in Bread4**",
"token_count": 1016,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Although many quantitative applications of acid–base titrimetry have been replaced by other analytical methods, there are several important applications that continue to be listed as standard methods. In this section we review the general application of acid–base titrimetry to the analysis of inorganic and organic comp... | {
"Header 1": "**9B.5 Quantitative Applications**",
"token_count": 2025,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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Alternatively, NO3 – can be titrated as a weak base in an acidic nonaqueous solvent such as anhydrous acetic acid, using HClO4 as a titrant.
Acid–base titrimetry continues to be listed as the standard method for the determination of alkalinity, acidity, and free CO2 in water and wastewater analysis. **Alkalinity** is... | {
"Header 1": "**9B.5 Quantitative Applications**",
"token_count": 1021,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
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| Source of Alkalinity | Relationship Between End Point Volumes |
|-------------------------|----------------------------------------|
| OH– | = VpH 8.3<br>VpH 4.5 |
| 2–<br>CO3 | VpH 4.5<br>= 2 × VpH 8.3 |
| –<br>HCO3 | VpH 8.3<br>= 0; ... | {
"Header 1": "**Table 9.8 Relationship Between End Point Volumes and Sources of Alkalinity**",
"token_count": 1991,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
For example, a procedure for determining the amount of nutritionally available protein has been developed that is based on an acid–base titration of lysine residues.<sup>6</sup>
<sup>&</sup>lt;sup>b</sup>The acetylation reaction, [1], is carried out in pyridine to avoid the hydrolysis of acetic anhydride by water. Af... | {
"Header 1": "**Table 9.8 Relationship Between End Point Volumes and Sources of Alkalinity**",
"token_count": 796,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The purity of a pharmaceutical preparation of sulfanilamide, $C_6H_4N_2O_2S$ , can be determined by oxidizing the sulfur to $SO_2$ and bubbling the $SO_2$ through $H_2O_2$ to produce $H_2SO_4$ . The acid is then titrated with a standard solution of NaOH to the bromothymol blue end point, where both of sulfuric ... | {
"Header 1": "**Table 9.8 Relationship Between End Point Volumes and Sources of Alkalinity**",
"Header 3": "EXAMPLE 9.3",
"token_count": 600,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The amount of protein in a sample of cheese is determined by a Kjeldahl analysis for nitrogen. After digesting a 0.9814-g sample of cheese, the nitrogen is oxidized to NH<sub>4</sub><sup>+</sup>, converted to NH<sub>3</sub> with NaOH, and distilled into a collection flask containing 50.00 mL of 0.1047 M HCl. The excess... | {
"Header 1": "**Table 9.8 Relationship Between End Point Volumes and Sources of Alkalinity**",
"Header 3": "EXAMPLE 9.4",
"token_count": 1906,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Table 9.11 Relationship Between End Point Volumes for Solutions of Phosphate Species with HCl and NaOH
| Solution<br>Composition | Relationship Between End Point<br>Volumes with Strong Base Titrant <sup>a</sup> | Relationship Between End Point<br>Volumes with S... | {
"Header 1": "**Table 9.8 Relationship Between End Point Volumes and Sources of Alkalinity**",
"Header 3": "EXAMPLE 9.4",
"token_count": 2013,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
At the other extreme, if the acid is too weak, the equilibrium constant for the titration reaction
$$HA(aq) + OH^{-}(aq) \rightleftharpoons H_2O(\ell) + A^{-}(aq)$$
may be so small that less than 50% of HA will have reacted at the equivalence point. In this case the concentration of HA before the equivalence point ... | {
"Header 1": "**Table 9.8 Relationship Between End Point Volumes and Sources of Alkalinity**",
"Header 3": "EXAMPLE 9.4",
"token_count": 467,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
**Scale of Operation** In an acid–base titration the volume of titrant needed to reach the equivalence point is proportional to the absolute amount of analyte present in the analytical solution. Nevertheless, the change in pH at the equivalence point, and thus the utility of an acid–base titration, is a function of the... | {
"Header 1": "**9B.8 Evaluation of Acid–Base Titrimetry**",
"token_count": 2024,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Conversely, if the acid dissociation constants for the analyte and interferent are similar, then an accurate end point for the analyte may not be found (Figure 9.24b). In the latter case, a quantitative analysis for the analyte is not possible.
In the second limiting situation the analyte is a weaker acid or base tha... | {
"Header 1": "**9B.8 Evaluation of Acid–Base Titrimetry**",
"token_count": 454,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The earliest titrimetric applications involving metal–ligand complexation were the determinations of cyanide and chloride using, respectively, Ag+ and Hg2+ as titrants. Both methods were developed by Justus Liebig (1803–1873) in the 1850s. The use of a monodentate ligand, such as Cl– and CN–, however, limited the utili... | {
"Header 1": "**9C Titrations Based on Complexation Reactions**",
"token_count": 1958,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Solving equation 9.12 for $[Y^{4-}]$ and substituting into the equation for the formation constant gives
$$K_{\rm f} = \frac{[{\rm CdY^{2-}}]}{[{\rm Cd^{2+}}]\alpha_{{\rm Y^{4-}}}C_{\rm EDTA}}$$
If we fix the pH using a buffer, then $\alpha_{Y^{4-}}$ is a constant. Combining $\alpha_{Y^{4-}}$ with $K_f$ giv... | {
"Header 1": "**9C Titrations Based on Complexation Reactions**",
"token_count": 2034,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
#### 9C.2 Complexometric EDTA Titration Curves
Now that we know something about EDTA's chemical properties, we are ready to evaluate its utility as a titrant for the analysis of metal ions. To do so we need to know the shape of a complexometric EDTA titration curve. In Section 9B we saw that an acid—base titration ... | {
"Header 1": "**9C Titrations Based on Complexation Reactions**",
"token_count": 1785,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
After adding 30.0 mL of EDTA, these concentrations are
$$[\text{CdY}^{2-}] = \frac{\text{initial moles Cd}^{2+}}{\text{total volume}} = \frac{M_{\text{Cd}}V_{\text{Cd}}}{V_{\text{Cd}} + V_{\text{EDTA}}}$$
$$= \frac{(5.00 \times 10^{-3} \text{ M})(50.0 \text{ mL})}{50.0 \text{ mL} + 30.0 \text{ mL}} = 3.13 \times 10^{... | {
"Header 1": "**9C Titrations Based on Complexation Reactions**",
"token_count": 1141,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Sketch the titration curve for 50.0 mL of 5.00 × 10–3 M Cd2+ with 0.010 M EDTA at a pH of 10, and in the presence of an ammonia concentration that is held constant throughout the titration at 0.010 M. This is the same titration for which we previously calculated the titration curve (Table 9.15 and Figure 9.27).
#### ... | {
"Header 1": "**EXAMPLE 9.7**",
"token_count": 653,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The equivalence point of a complexation titration occurs when stoichiometrically equivalent amounts of analyte and titrant have reacted. For titrations involving metal ions and EDTA, the equivalence point occurs when *C*<sup>M</sup> and *C*EDTA are equal and may be located visually by looking for the titration curve's ... | {
"Header 1": "**9C.3 Selecting and Evaluating the End Point**",
"token_count": 2032,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Eriochrome Black T or calmagite is used as a visual indicator. Hardness is reported in parts per million CaCO<sub>3</sub>.
**Procedure.** Select a volume of sample requiring less than 15 mL of titrant to keep the analysis time under 5 min and, if necessary, dilute the sample to 50 mL with distilled water. Adjust the ... | {
"Header 1": "**9C.3 Selecting and Evaluating the End Point**",
"token_count": 814,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
With a few exceptions, most quantitative applications of complexation titrimetry have been replaced by other analytical methods. In this section we review the general application of complexation titrimetry with an emphasis on selected applications from the analysis of water and wastewater. We begin, however, with a dis... | {
"Header 1": "**9C.5 Quantitative Applications**",
"token_count": 2041,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Report the weight percents of Ni, Fe, and Cr in the alloy.
#### SOLUTION
Conservation of electron pairs for the three titrations requires that for
Titration 1: moles Ni = moles EDTA1 (Fe, Cr masked)
Titration 2: moles Ni + moles Fe = moles EDTA2 (Cr masked)
Titration 3: moles Ni + moles Fe + moles Cr + moles ... | {
"Header 1": "**9C.5 Quantitative Applications**",
"token_count": 1076,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The scale of operations, accuracy, precision, sensitivity, time, and cost of methods involving complexation titrations are similar to those described earlier for acid–base titrimetric methods. Compared with acid–base titrations, however, complexation titrations are more selective. Despite the ability of EDTA to form st... | {
"Header 1": "9C.6 Evaluation of Complexation Titrimetry",
"token_count": 423,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
A titration in which the reaction between the analyte and titrant is an oxidation/reduction reaction. The number of redox titrimetric methods increased in the mid-1800s with the introduction of $MnO_4^-$ , $Cr_2O_7^{2-}$ and $I_2$ as oxidizing titrants, and $Fe^{2+}$ and $S_2O_3^{2-}$ as reducing titrants. Eve... | {
"Header 1": "redox titration",
"token_count": 2034,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
We can, however, calculate
$E_{\text{eq}}$ by combining the two Nernst equations. To do so we recognize that the potentials for the two half-reactions are the same; thus,
$$E_{\text{eq}} = E_{\text{Fe}^{3+}/\text{Fe}^{2+}}^{\circ} - 0.05916 \log \frac{[\text{Fe}^{2+}]}{[\text{Fe}^{3+}]}$$
$$E_{\text{eq}} = E_{\t... | {
"Header 1": "redox titration",
"token_count": 1592,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Sketch a titration curve for the titration of 50.0 mL of 0.100 M Fe2+ with 0.100 M Ce4+ in a matrix of 1 M HClO4. This is the same titration for which we previously calculated the titration curve (Table 9.17 and Figure 9.34).
#### *SOLUTION*
We begin by drawing axes for the titration curve (Figure 9.35a). Having sh... | {
"Header 1": "**EXAMPLE 9.11**",
"token_count": 2023,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
In acidic solutions, however, permanganate's reduced form, $Mn^{2+}$ , is nearly colorless. When $MnO_4^-$ is used as an oxidizing titrant, the solution remains colorless until the first drop of excess $MnO_4^-$ is added. The first permanent tinge of purple signals the end point.
A few substances indicate the pr... | {
"Header 1": "**EXAMPLE 9.11**",
"token_count": 1156,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
*Description of the Method.* The chlorination of public water supplies results in the formation of several chlorine-containing species, the combined concentration of which is called the total chlorine residual. Chlorine may be present in a variety of states including free residual chlorine, consisting of Cl2, HOCl, and... | {
"Header 1": "**Method 9.3 Determination of Total Chlorine Residual13**",
"token_count": 650,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
As with acid–base and complexation titrations, redox titrations are not frequently used in modern analytical laboratories. Nevertheless, several important applications continue to find favor in environmental, pharmaceutical, and industrial laboratories. In this section we review the general application of redox titrime... | {
"Header 1": "**9D.4 Quantitative Applications**",
"token_count": 2042,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
#### **Titration Reaction**
$$\begin{split} \text{Ce}^{4+} + \text{Fe}^{2+} &\rightarrow \text{Ce}^{3+} + \text{Fe}^{3+} \\ 2\text{Ce}^{4+} + \text{H}_2\text{C}_2\text{O}_4 + 2\text{H}_2\text{O} &\rightarrow 2\text{Ce}^{3+} + 2\text{CO}_2 + 2\text{H}_3\text{O}^+ \\ \text{MnO}_4^- + 5\text{Fe}^{2+} + 8\text{H}_3\text{... | {
"Header 1": "**Table 9.20 Standardization Reactions for Selected Redox Titrants**",
"token_count": 2020,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
When a sample of iodide-free chlorinated water is mixed with an excess of the indicator *N*,*N*-diethyl-*p*-phenylenediamine (DPD), the free chlorine oxidizes a stoichiometric portion of DPD to its red-colored form. The oxidized DPD is then titrated back to its colorless form with ferrous ammonium sulfate, with the vol... | {
"Header 1": "**Table 9.20 Standardization Reactions for Selected Redox Titrants**",
"token_count": 2037,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
For example, treatment of serine with $IO_4^-$ results in the following oxidation reaction
$$\begin{array}{cccccccccccccccccccccccccccccccccccc$$
The analysis is conducted by adding a known excess of $IO_4^-$ to the solution containing the analyte and allowing the oxidation to take place for approximately 1 h a... | {
"Header 1": "**Table 9.20 Standardization Reactions for Selected Redox Titrants**",
"token_count": 1155,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
#### EXAMPLE 9.14
A 25.00-mL sample of a liquid bleach was diluted to 1000 mL in a volumetric flask. A 25-mL portion of the diluted sample was transferred by pipet into an Erlenmeyer flask and treated with excess KI, oxidizing the OCl<sup>-</sup> to Cl<sup>-</sup>, and producing I<sub>3</sub><sup>-</sup>. The liberat... | {
"Header 1": "0",
"token_count": 2035,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Thus far we have examined titrimetric methods based on acid—base, complexation, and redox reactions. A reaction in which the analyte and titrant form an insoluble precipitate also can form the basis for a titration. We call this type of titration a **precipitation titration**.
One of the earliest precipitation titrat... | {
"Header 1": "**9E Precipitation Titrations**",
"token_count": 1617,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
| Volume AgNO <sub>3</sub> | | |
|--------------------------|------|------|
| (mL) | pCl | pAg |
| 0.00 | 1.30 | _ |
| 5.00 | 1.44 | 8.31 |
| 10.00 | 1.60 | 8.14 |
| 15.00 | 1.81 | 7.93 |
| 20.00 ... | {
"Header 1": "Table 9.21 Data for Titration of 50.0 mL of 0.0500 M Cl<sup>-</sup> with 0.100 M Ag<sup>+</sup>",
"token_count": 823,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Initial attempts at developing precipitation titration methods were limited by a poor end point signal. Finding the end point by looking for the first addition of titrant that does not yield additional precipitate is cumbersome at best. The feasibility of precipitation titrimetry improved with the development of visual... | {
"Header 1": "**9E.2 Selecting and Evaluating the End Point**",
"token_count": 700,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Precipitation titrimetry is rarely listed as a standard method of analysis, but may still be useful as a secondary analytical method for verifying results obtained by other methods. Most precipitation titrations involve Ag+ as either an analyte or
| | of Precipitation Ti ... | {
"Header 1": "**9E.3 Quantitative Applications**",
"token_count": 2000,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
| acid–base titration (p. 278) |
|-------------------------------------|
| acidity (p. 301) |
| alkalinity (p. 300) |
| argentometric titration (p. 355) |
| auxiliary complexing agent (p. 316) |
| auxiliary oxidizing agent (p. 341) |
| auxiliary reducing agent (p. 341) |
... | {
"Header 1": "F KEY TERMS",
"token_count": 372,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
In a titrimetric method of analysis the volume of titrant reacting stoichiometrically with the analyte provides quantitative information about the amount of analyte in a sample. The volume of titrant required to achieve this stoichiometric reaction is called the equivalence point. Experimentally we determine the titrat... | {
"Header 1": "**9G SUMMARY**",
"token_count": 384,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
*The following experiments may be used to illustrate the application of titrimetry to quantitative, qualitative, or characterization problems. Experiments are grouped into four categories based on the type of reaction (acid–base, complexation, redox, and precipitation). A brief descripti... | {
"Header 1": "**9H** *Suggested* **EXPERIMENTS**",
"token_count": 2037,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The titration is followed spectrophotometrically by measuring the absorbance of a visual indicator. The effect of changing the indicator, the pH at which the titration is carried out, and the relative concentrations of Ca<sup>2+</sup> and Mg<sup>2+</sup> are also investigated.
Novick, S. G. "Complexometric Titration ... | {
"Header 1": "**9H** *Suggested* **EXPERIMENTS**",
"token_count": 532,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Continued from page 359
Haddad, P. "Vitamin C Content of Commercial Orange Juices," *J. Chem. Educ.* **1977**, *54*, 192–193.
The content of ascorbic acid, in milligrams per 100 mL, in orange juice is determined by a redox titration using either 2,6-dichlorophenolindephenol or *N*-bromosuccinimide as the titrant. ... | {
"Header 1": "xperiments",
"token_count": 1389,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
| Volume NaOH | | Volume NaOH | |
|-------------|-----|-------------|------|
| (mL) | pH | (mL) | pH |
| 0.25 | 3.0 | 49.97 | 8.0 |
| 0.86 | 3.2 | 49.98 | 8.2 |
| 1.63 | 3.4 | 49.99 | 8.4 |
| 2.72 | 3.6 | 50.00 | 8.7 |
| 4.29 | 3... | {
"Header 1": "xperiments",
"token_count": 1998,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Two drops of a methyl violet visual indicator are added, and the solution is titrated with previously standardized 0.1000 M HClO4 (prepared in glacial acetic acid using anhydrous HClO4) until the visual end point is reached. Results are reported as parts per million of aniline.
- (a) Explain why this titration is condu... | {
"Header 1": "xperiments",
"token_count": 1969,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
| | Titrant | Volume (mL) to the<br>Phenolphthalein<br>End Point | Volume (mL) to the<br>Methyl Orange<br>End Point |
|-----|---------|----------------------------------------------------|--------------------------------------------------|
| (a) | HCl | 11.54 | 35.... | {
"Header 1": "xperiments",
"token_count": 2019,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
(d) Samples of KHP are weighed into separate Erlenmeyer flasks, but the balance is only tared with the first flask. (e) The KHP was not dried before it was used. (f) The NaOH was not dried before it was used. (g) The procedure calls for the sample of KHP to be dissolved in 25 mL of water, but it is accidentally dissolv... | {
"Header 1": "xperiments",
"token_count": 1953,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
Prada and colleagues recently described a new indirect method for determining sulfate in natural samples, such as sea water and industrial effluents.16 The method is based on (1) precipitating the sulfate as PbSO4; (2) dissolving the PbSO4 in an ammonical solution of excess EDTA to form the soluble PbY2– complex; and (... | {
"Header 1": "xperiments",
"token_count": 2029,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
The resulting solution is then titrated with a standard solution of KMnO<sub>4</sub> until a faint pink color persists for 30 s. The results are reported as %w/v $H_2O_2$ .
- (a) Many commercially available solutions of H<sub>2</sub>O<sub>2</sub> contain an inorganic or organic stabilizer to prevent the autodecomposit... | {
"Header 1": "xperiments",
"token_count": 2047,
"source_pdf": "datasets/websources/biochem/Modern analytical chemistry by David Harvey.pdf"
} |
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