Analytical Chemistry

    ❒ When a weak acid or a weak base is dissolved in water, partial dissociation occurs. Thus, for nitrous acid, we can write:   where Ka is the acid dissociation constant for nitrous acid. ❒In an analogous way, the base dissociation constant for ammonia is   ❒Notice that …

      ❒Many organic reactions involve the transfer of a proton by an acid–base reaction. An important consideration, therefore, is the relative strengths of compounds that could potentially act as Brønsted–Lowry acids or bases in a reaction. ❒In contrast to the strong acids, such as HCl and H2SO4, acetic …

  Solubility-Product Constants ** Most, but not all, sparingly soluble salts are essentially completely dissociated in saturated aqueous solution.  ** For example, when an excess of barium iodate is equilibrated with water, the dissociation process is adequately described by the equation:   Using Equation:     we write:     …

  Dilution of Solutions   ** Concentrated solutions are often stored in the laboratory stockroom for use as needed. Frequently we dilute these “stock” solutions before working with them.  ** Dilution is the procedure for preparing a less concentrated solution from a more concentrated one. ** Suppose that we want …

  To study solution stoichiometry, we must know how much of the reactants are present in a solution and also how to control the amounts of reactants used to bring about a reaction in aqueous solution. The concentration of a solution   ** The concentration of a solution is the …

  Chemical Equilibrium   ** Many reactions used in analytical chemistry never result in complete conversion of reactants to products. Instead, they proceed to a state of chemical equilibrium in which the ratio of concentrations of reactants and products is constant. ** Equilibrium- constant expressions are algebraic equations that describe …

    Water is the most plentiful solvent on Earth, is easily purified, and is not toxic. It is, therefore, widely used as a medium for chemical analyses. Classifying Solutions of Electrolytes   ** Most of the solutes we will discuss are electrolytes, which form ions when dissolved in water …

  Chemical Stoichiometry ** Stoichiometry is the quantitative relationship among the amounts of reacting chemical species. ** This subject provides a brief review of stoichiometry and its applications to chemical calculations. ** The stoichiometry of a reaction is the relationship among the number of moles of reactants and products as …

    ** Over the course of history, measurements and their corresponding units were invented at the local level. By necessity of primitive communication and local technology, standards were nearly nonexistent, and conversions among the many systems were difficult. The result was many hundreds of distinct ways of expressing concentrations …

  SI Units   ** Scientists throughout the world have adopted a standardized system of units known as the International System of Units (SI). ** This system (SI) is based on the seven fundamental base units shown in Table (1). Table (1) ** Numerous other useful units, such as volts, …

  Safety In The Laboratory There is necessarily a degree of risk associated with any work in a chemical laboratory.  Accidents can and do happen. Strict adherence to the following rules will go far toward preventing (or minimizing the effect of ) accidents: (1)Before you begin work in any laboratory, …

  The Laboratory Notebook   ** A laboratory notebook is needed to record measurements and observations concerning an analysis. ** The book should be permanently bound with consecutively numbered pages (if necessary, the pages should be hand numbered before any entries are made). ** Most notebooks have more than ample …

  Calibrating Volumetric Glassware   ** Volumetric glassware is calibrated by measuring the mass of a liquid (usually distilled or deionized water) of known density and temperature that is contained in (or delivered by) the volumetric ware. ** In carrying out a calibration, a buoyancy correction must be made since the density …

  Volumetric Flasks ** Volumetric flasks are manufactured with capacities ranging from 5 mL to 5 L and are usually calibrated to contain (TC) a specified volume when filled to a line etched on the neck.      ** They are used for the preparation of standard solutions and for the dilution …

Pipets ** Pipets permit the transfer of accurately known volumes from one container to another. ** Common types are shown in Figure (1), and information concerning their use is given in Table (1).    Table (1) ** A volumetric, or transfer, pipet (Figure 1a) delivers a single, fixed volume between 0.5 and 200 …

Burets ** Burets, like measuring pipets, make it possible to deliver any volume up to the maximum capacity of the device. The precision attainable with a buret is substantially greater than the precision with a pipet. ** A buret consists of a calibrated tube to hold titrant plus a valve arrangement by …

    The precise measurement of volume is as important to many analytical methods as the precise measurement of mass. (1) Units of Volume   ** The unit of volume is the liter (L), defined as one cubic decimeter. ** The milliliter (mL) is one one-thousandth of a liter (0.001 …

  Several techniques and experimental arrangements allow solids to be filtered and ignited with minimal contamination and error. (1) Apparatus (a) Simple Crucibles   ** Simple crucibles serve only as containers. Porcelain, aluminum oxide, silica, and platinum crucibles maintain constant mass—within the limits of experimental error— and are used principally to …

  Percent Composition of Compounds **As we have seen, the formula of a compound tells us the numbers of atoms of each element in a unit of the compound. ** However, suppose we needed to verify the purity of a compound for use in a laboratory experiment. We could calculate …

  Total  and partial ionization ** When an acid or base is dissolved in water, it will dissociate, or ionize According to the equations:  ** The amount of ionization being dependent on the strength of the acid or the base.  ** A “strong” electrolyte is completely dissociated, while a “weak” electrolyte is partially …