Performing a Titration

It is possible to determine the concentration of certain metal ions by performing a titration in which the complexation of the metal is the essential reaction. Typically, a chelating agent such as EDTA is used because the complexes formed are so stable. The specific composition of complexes formed in solutions often depends on the concentrations of the reactants. As a part of the study of the chemistry of coordination compounds, some attention must be given to the systematic treatment of topics related to the composition and stability of complexes in solution. This chapter is devoted to these topics. 

FIGURE 4.15 The correct way for a right-handed person to position his or her hands when performing a titration. 

In Investigation 8-A, you performed a titration and graphed the changes in the pH of acetic acid solution as sodium hydroxide solution was added. A graph of the pH of an acid (or base) against the volume of an added base (or acid) is called an acid-base titration curve. 

In this section, you will learn how to predict the pH of an aqueous solution of a salt. Predicting the pH is useful when you are performing a titration experiment, because you need to choose an indicator that changes colour at a pH value that is close to the pH at equivalence. 

A student performed a titration of a weak, monoprotic acid, HA, with a sodium hydroxide, NaOH, solution. 

Precise volume measurements are needed when you perform a titration. Chemists use special glass apparatus to collect these measurements. (See Figure 10.15.) As well, an acid-base indicator is needed to monitor changes in pH during the titration. 

A student performed a titration using 2.00 M HC1 to completely titrate 40.00 mL of 1.00 MNaOH. If the initial reading on the buret containing HC1 was 2.05 mL, what will the final reading of this buret be ... 

PROBLEM A student is performing a titration in the laboratory. She delivers 15.00 mL of HCl of an unknown molarity to a flask via a buret. She then adds... 

A student performs a titration using 1.00 M NaOH to find the unknown molarity of a solution of HC1. The student records the data as shown below. What is the molarity of the solution of HC1 ... 

The gradual addition of one solution to another to reach an equivalence point is called a titration. The purpose of a titration is to determine the concentration of an acid or a base. In addition to the two solutions, the equipment needed to carry out a titration usually includes two burets, a titration flask, and a suitable indicator. Skills Toolkit 1, later in this section, will describe how this equipment is used to perform a titration. 

Skills Toolkit 1, on the next two pages, has step-by-step instructions to help you carry out an acid-base titration. Study and understand all of the steps before you start to perform a titration experiment. If your attention alternates between book and buret, you re likely to make mistakes. Experience helps, and your second titration should be much better than your first. 

Design an Experiment Describe how you would design and perform a titration in which you use 0.250M HNO3 to determine the molarity of a cesium hydroxide solution. Include the formula and net ionic equations. 

The concentration of free ligand [L]p, or the concentration of bound ligand [L]b is measured, as the [LJt is added. It is important to remember that the number of binding sites on a protein molecule is not known initially, so even if its molar concentration is known, the concentration of the sites is not. The protein may be even a crude and impure preparation of a cell extract this is not problematic because only a knowledge of the total ligand concentration and the free or bound ligand concentrations can be used to perform a titration. 

For accurate results, it is advisable to control the surfactant adsorption performing a titration. The effluent leaving the column is collected until the detector response reaches a plateau corresponding to the absorbance value of the initial surfactant solution. The surfactant concentration in die collected effluent is determined by titration. The missing surfactant mass is adsorbed on the stationary phase in the column. The mass obtained by titration should corroborate the one obtained using the breakthrough volume. 

One way of determining blood alcohol levels is by performing a titration on a sample of blood. In this process, the alcohol from the blood is oxidized by dichromate ions (Cr207 ) according to the following net ionic equation ... 

Due to large variations in the extent of cellular transcription between developmental time points, specific tissues, or states, it is useful to perform a titration experiment to determine the likely amount of total RNA expected per mg of tissue or per cell. 

Whenever you perform a titration calculation, be sure that you have taken into account the stoichiometry of the reaction between the acid and base (use the balanced chemical equation). In this case, two moles of NaOH are required to neutralize each mole of acid. Furthermore, when performing titration calculations, do not be tempted to apply the dilution equation to solve the problem. If you were to take such an approach here, you would arrive at an incorrect result since the dilution equation fails to take into account the stoichiometry of the reaction. 

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