Volumetric analysis calculations

Volumetric analysis - calculating the concentration of a test substance... 

Here are some examples to illustrate stoichiometry calculations in volumetric analysis. The key step is to relate moles of titrant to moles of analyte. We also introduce the Kjeldahl titration as a representative volumetric procedure. 

The validity of an analytical result depends on knowing the amount of a primary standard. A solution with an approximately desired concentration can be standardized by titrating a primary standard. In a direct titration, titrant is added to analyte until the reaction is complete. In a back titration, a known excess of reagent is added to analyte, and the excess is titrated with a second standard reagent. Calculations of volumetric analysis relate the known moles of titrant to the unknown moles of analyte. 

At 14.7 psia and 32°F, 1 mol of any gas occupies 359 ft3. The volume per pound of any gas at these conditions can be found by dividing 359 by the molecular weight of the gas and correcting for the gas temperature by multiplying the volume by the ratio of the absolute flue-gas temperature and the atmospheric temperature. To change the weight analysis (step 3) of the products of combustion to volumetric analysis, set up the calculation thus ... 

The composition of the gas is given on a volumetric basis, which is the usual way of expressing a fuel-gas analysis. To use the volumetric-analysis data in combustion calculations, they must be converted to a weight basis. This is done by dividing the weight of each component by the total weight of the gas. A volume of 1 ft3 of the gas is used for this computation. Find the weight of each... 

Examples of the types of calculations used in volumetric analysis are shown in Box 21.1. 

Factors are used in volumetric analysis because they simplify calculations (a laudable aim, in any subject). Consider the first solution above the strength of the solution is 1 m (1.026). If 10 mL of this solution were removed, by pipette, transferred to a 100 mL volumetric flask, and made up to volume with water, the resulting solution would have a concentration of 0.1 M (1.026). The original solution has been diluted tenfold, but the factor of the new solution remains as 1.026. This illustrates an important principle, namely, that once a factor has been determined for a volumetric solution, subsequent dilution or reaction will not affect it (although see later for an exception to this). 

Sources of error can be introduced in each conversion from volume to moles and back to weight, although for simple examples such as the one above it does not really matter which method of calculation is employed as long as the correct answer for the purity of citric acid is obtained. However, for more complicated calculations, involving the use of back and blank titrations, this author believes that factors and equivalents simplify volumetric analysis and they will be used for that reason (rather than any reason of dogma) in the remainder of this book. 

Calculations of volumetric analysis ordinarily consist of transforming the quantity of titrant used (in chemical units) to a chemically equivalent quantity of analyte (also in chemical units) through use of a stoichiometric factor. Use chemical formulas (NO CALCULATIONS REQUIRED) to express this ratio for calculation of the percentage of (a) hydrazine in rocket fuel by titration with standard iodine. Reaction ... 

In this chapter we review the fundamental concepts of mass, moles, and equivalents the ways in which analytical results may be expressed for solids and liquids and the principles of volumetric analysis and how stoichiometric relationships are used in titrations to calculate the mass of analyte. 

Molarity and normality are the most useful concentrations in quantitative See Sections 5.5 and 5.6 for volu-analysis. Calculations using these for volumetric analysis are discussed in more metric calculations using molarity or detail below. normality. 

The calculations in volumetric analysis require that the balanced reaction be known. The balancing of redox reactions is reviewed in your CD. 

The principle upon which volumetric analysis is based is that by determining the volume of a solution of known strength, required to accurately neutralize another solution of unkno-w-n strength, the amount of active substance in the latter may be calculated. 

The Third Edition includes more foundation work un formulae, the mole, calculations based on chemical equations and volumetric analysis for students starting A/AS Work from National Curriculum GCSE Science Double Award. 

The relationship between the emf of the cell and the number of milhliters of ceric salt added to the stannous solution is of the same form as Fig. 15.15. The equivalence point is denoted by a rapid change in potential as the ceric salt is added. If necessary, the first and second differentials of the curve may be taken to detect the endpoint as shown in Fig. 15.16. From the data obtained, calculations of solution concentrations and other variables are done in the same manner as in conventional volumetric analysis. 

What I have presented is the solution to a unique metering problem, where in order to measnre an ENRICHED S YNTHETIC NATURAL GAS stream, requires (in addition to a volumetric and heating value measurement) two gas chromatographic analyses to calculate the supercompressibility of the raw SNG and the heating value of the enriching LPG, one liquid volumetric analysis, and a specific gravity measnrement... 

I n volumetric analysis, the volume of a known reagent required for complete reaction with analyte by a known reaction is measured. From this volume and the stoichiometry of the reaction, we calculate how much analyte is in an unknown substance. In this chapter we discuss general principles that apply to any volumetric procedure, and then we illustrate some analyses based on precipitation reactions. Along the way, we introduce the solubility product as a means of understanding precipitation reactions. 

Carl Friedrich Mohr (Coblenz, 4 November 1806-Bonn, 28 September 1879), at first an apothecary in Coblenz then associate professor of pharmacy in Bonn, published many papers and a book on pharmacy, describing new apparatus. Mohr was one of the pioneers of volumetric analysis. He also wrote on the mechanical theory of heat and chemical afimity. He sa rs in (i) heat is no longer a substance, but is rather an oscillatory motion of the smallest parts (rather like Davy s theory) he used (like Mayer in 1842) the name E aft for energy, and said heat is a form of it. He pointed out the relation of the difference of the specific heats of air at constant volume and pressure to this nature of heat, but did not (as Mayer did) calculate the mechanical Equivalent of heat from it. He is an obscure writer and his later claims to have anticipated Clausius are unfounded, but he anticipated some of Mayer s ideas. He acted... 

To get a better feeling for these parameters, n = 1, j3p = 10 and b = 10 yield an error of 0.25%, larger than that of volumetric analysis. These theoretical errors were calculated without taking the dilution effect into consideration. Taking this into ac count, in choosing a titration procedure with which one hopes to attain an error of better than 0.1%, one should make sure that Y < 10" orb < 70 . The errors... 

The following analysis enables one to calculate the diameter of a pipeline transporting any compressible fluid. The required inputs are volumetric flow rate, the specific gravity of the gas relative to air, flow conditions, compressibility factor Z where Z is defined by nZRT = PV, the pressure at the point of origin and the destination, the pipe length, and pipe constants such as effective roughness. The working equations have been obtained from the literature. Since the friction factor... 

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