SOLUTION STOICHIOMETRY AND CHEMICAL ANALYSIS

Either way, we see that if we start with 15 mL of 3.0 M H2SO4 and dilute it to a total volume of450 mL, the desired 0.10 M solution will be obtained. 

Check The calculated volume seems reasonable because a small volume of concentrated solution is used to prepare a large volume of dilute solution. 

Comment The first approach can also be used to find the final concentration when two solutions of ddferent concentrations are mixed, whereas the second approach, using Equation 4.34, 

What volume of a 1.00 M stock solution of glucose must be used to make 500.0 mL of a 1.75 X 10 M glucose solution in water  

In Chapter 3 we learned that given the chemical equation for a reaction and the amount of one reactant consumed in the reaction, you can calculate the quantities of other reactants and products. In this section we extend this concept to reactions involving solutions. 

Recall that the coefficients in a balanced equation give the relative number of moles of reactants and products. (Section 3.6) To use this information, we must convert 

How many grams of Ca(OH)2 are needed to neutralize 25.0 mL of 0.100 M HNOj SOLUTION 

Analyze The reactants are an add, HNO3, and a base, Ca(OH)2- The volume and molarity of HNO3 are given, and we are asked how many grams of Ca(OH)2 are needed to neutralize this quantity of HNO3. 

Solve The product of the molar concentration of a solution and its volume in liters gives the number of moles of solute  

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SOLUTION STOICHIOMETRY AND CHEMICAL ANALYSIS We see how the concepts of stoichiometry and concentration can be used to calculate amounts or concentrations of substances in solution through a common chemical practice called titration. 

SOLUTION STOICHIOMETRY AND CHEMICAL ANALYSIS (SECTION 4.6) In the process called titration, we combine a solution of known concentration (a standard solution) with a solution of unknown concentration to determine the unknown concentration or the quantity of solute in the unknown. The point in the titration at which stoichiometricaUy equivalent quantities of reactants are brought together is called the equivalence point. An indicator can be used to show the end point of the titration, which coincides closely with the equivalence point. 

Gravimetric analysis utilizes primarily weight measurements and may or may not involve chemical reactions. Titrimetric analysis utilizes both weight and volume measurements and always involves solution chemistry and stoichiometry. 

The chemical etch rate of a material by an etchant depends on the solution temperature, surface area (him morphology), residual him stress, him microstructure, stoichiometry, and the soluhon strength. It also dq)cnds on how fast the etch products arc removed from the surface and from the vicinity of the surface (i.e. agitahon). Gradahon of him properties through the thickness can also affect the etch rate. Chemical etch rates are primarily used as comparahve tests. Figure 11.7 shows a typical etch rate analysis and Table 3.11 Usts chemical etchants for a number of materials many more are to be found in the literature. 

This method is primarily based on measurement of the electrical conductance of a solution from which, by previous calibration, the analyte concentration can be derived. The technique can be used if desired to follow a chemical reaction, e.g., for kinetic analysis or a reaction going to completion (e.g., a titration), as in the latter instance, which is a conductometric titration, the stoichiometry of the reaction forms the basis of the analysis and the conductometry, as a mere sensor, does not need calibration but is only required to be sufficiently selective. 

Widespread medicinal use of colloidal bismuth subcitrate (CBS) has prompted extensive studies of bismuth compounds involving the citrate anion. Bismuth citrate is essentially insoluble in water, but a dramatic increase in solubility with increasing pH has been exploited as a bio-ready source of soluble bismuth, a material referred to as CBS. Formulation of these solutions is complicated by the variability of the bismuth anion stoichiometry, the presence of potassium and/ or ammonium cations, the susceptibility of bismuth to oxygenation to Bi=0, and the incorporation of water in isolated solids. Consequently, a variety of formulas are classified in the literature as CBS. Solids isolated from various, often ill-defined combinations of bismuth citrate, citric acid, potassium hydroxide, or ammonium hydroxide have been assigned formulas on the basis of elemental analysis data or by determination of water and ammonia content, but are of low significance in the absence of complementary data other than thermal analysis (163), infrared spectroscopy (163), or NMR spectroscopy (164). In this context, the Merck index lists the chemical formula of CBS as KgfNHJaBieOafOHMCeHsCbh in the 11th edition (165), but in the most recent edition provides a less precise name, tripotassium dicitrato bismuthate (166). 

Titration — A process for quantitative analysis in which measured increments of a - titrant are added to a solution of an - analyte until the reaction between the analyte and titrant is considered as complete at the - end point [i]. The aim of this process is to determine the amount of an analyte in a -> sample. In addition, the determination can involve the measurement of one or several physical and/or chemical properties from which a relationship between the measured parameter/s and the concentration of the analyte is established. It is also feasible to measure the amount of a - titrand that is added to react with a fixed volume of titrant. In both cases, the -> stoichiometry of the reaction must be known. Additionally, there has to be a means such as a -> titration curve or an - indicator to recognize that the -> end point has been reached. The nature of the reaction between the titrant and the analyte is commonly indicated by terms like acid-base, complexometric, redox, precipitation, etc. [ii]. Titrations can be performed by addition of measured volume/mass increments of a solution,... 

Solution NMR spectroscopy is the most widely used technique to determine the equihbrium constant of supramolecular polymers [23,24,59,123, 148,149,158,197], either directly or with the help of a monofunctional model compound, hi the usual case of a fast exchange between free and hydrogen bonded extremities, the equihbrium constants of a particular association model are derived from the analysis of the evolution of the chemical shift versus concentration (for self-complementary functions) or versus stoichiometry (for complementary functions). Equihbrium constants in the range below 10 are reliably accessible. 

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