Acid-base titrations neutralization titration

Alkalinity is measured by acid-base titration with methylorange or phe-nolphthalein as indicator. Phenolphthalein changes color at pH 8.3, whereas methylorange changes color at pH 4.3. At pH 8 the neutralization of the strong alkali ingredients like NaOH is essentially complete. Further reduction of the pH to 4 will also measure carbonates and bicarbonates. Colorimetric tests and glass electrode systems are used to determine pH. 

Scenario A student measured out approximately 10 mL of 6.00 M NaOH and diluted the base to approximately 600 mL. The student then performed an acid-base titration (see Figure 3) and determined that 48.7 mL of NaOH solution were needed to neutralize 50.0 mL of a 0.100 M HC1 solution. 

One important application of acid-base titrations is the determination of the alkalinity of various kinds of samples. It is an especially important measurement for the proper treatment of municipal water and wastewater. Alkalinity of a water sample is defined as its acid-neutralizing capacity. It is determined by titrating the water sample with standard acid until a particular pH is achieved. The alkalinity value... 

In this experiment the neutralizing power of various antacids will be determined. Antacids contain basic compounds that will neutralize stomach acid (stomach acid is HC1). The amount of base in the antacid tablets will be determined by an acid-base titration. It is a back titration method. This method is used because most antacids produce carbon dioxide gas, which can interfere with the titration. By initially adding an excess of acid, one can drive off the C02 by boiling the solution before titrating the excess acid. There are many brands of commercial antacids with various ingredients. A few of the common ones are listed below ... 

Elemental composition Cs 88.65%, H 0.67%, O 10.67%. CsOH can be standardized by acid-base titration using HCl or H2SO4 and a color indicator, or by potentiometric titration to neutral pH. 

An acid-base titration is a method that allows quantitative analysis of the concentration of an unknown acid or base solution. In an acid-base titration, the base will react with the weak acid and form a solution that contains the weak acid and its conjugate base until the acid is completely neutralized. The following equation is used frequently when trying to find the pH of buffer solutions. 

For the titration of a strong base with a weak acid, the equivalence point is reached when the pH is greater than 7. The half equivalence point is when half of the total amount of base needed to neutralize the acid has been added. It is at this point that the pH = pK of the weak acid. In acid-base titrations, a suitable acid-base indicator is used to detect the endpoint from the change of colour of the indicator used. An acid-base indicator is a weak acid or a weak base. The following table contains the names and the pH range of some commonly used acid-base indicators. 

M. Cremer at the Institute of Physiology at Munich discovered in 1906 that a potential difference of 0.2 V developed across a glass membrane with acid on one side and neutral saline solution on the other. The student Klemensiewicz, working with F. Haber in Karlsruhe in 1908, improved the glass electrode and carried out the first acid-base titration to be monitored with a glass electrode.13... 

The pH of a solution at the stoichiometric point of an acid-base titration depends on the properties of the salt formed in the neutralization reaction. At the stoichiometric point of the titration of formic acid, HCOOH (1), with sodium hydroxide, the solution consists of sodium formate, NaHC02, and water. Formate ion, HC02 (2), is a base, and the Na+ ions have virtually no effect on pH so overall the solution is basic, even though the acid has been completely neutralized. 

A titration is a technique for determining the concentration of a material in solution by measuring the volume of a standard solution that is required to react with the sample. One of the most common titrations is the acid-base titration in which the concentration of a base can be determined by adding a standard solution of an acid to the sample until the base is exactly neutralized. The exact neutralization point is found by the use of an indicator that changes color when the end-point is reached. 

Acid-base titration involves a neutralization reaction between an acid and a soluble base. The reactants may be a strong acid and a strong base, a strong acid... 

In Figure 10.49 a computer calculation is given, simulating the gigantic acid-base titration that led to the formation of the neutralization products of ocean and sediments. The importance of this calculation is that it demonstrates the essence of equation 10.12 as primary igneous rock minerals react with water and acids, the excess volatiles, by reactions like ... 

In a typical acid-base titration, an acid-base indicator (such as phenolphthalein) or a pH meter is used to monitor the course of a neutralization reaction. The usual goal of titration is to determine an unknown concentration of an acid (or base) by neutralizing it with a known concentration of base (or acid). 

When the progression of an acid-base titration is graphed as a function of pH vs the volume of acid or base added, the curve will appear as shown below. If we recall, from general chemistry coursework, that the steepest point on the curve represents the equivalence point of the titration (the point where the amount of acid and base are equal), we can locate the point on the curve that represents the midpoint of the titration. This point is found at half the concentration of base added to acid (or acid added to base) to reach the equivalence point. Once we have done this, we recall the Henderson-Hesselbach equation (Fig. 2.8)—specifically, the term dealing with the concentrations of the ionic and the neutral species. Realizing that at the midpoint of the titration, these concentrations are equal, the logarithmic term in the Henderson-Hesselbach equation reduces to log(l), which is equal to zero. Therefore, the equation reduces to pA a = pH at the midpoint of the titration. 

Even if you cannot influence the sequence of data collection, you can control the size of the interval between points. The general rule is Take points more closely spaced when the observed quantity is varying more rapidly. Thus data points should be taken more frequently at early times for chemical kinetics and near the neutralization endpoint for an acid-base titration, as illustrated in Fig. 1. 

Calculate the concentration of H2SO4 solution that is completely neutralized in an acid-base titration if the concentration of NaOH solution is 1.500 M, the volume of H2SO4 solution is 25.00 mL, the initial buret reading for the NaOH solution is 1.28 mL, and the final buret reading is 45.19 mL. 

In order that a particular indicator may be of use for a given acid-base titration, it is necessary that its exponent should correspond to a pH on the almost vertical portion of the pH-neutralization curve. When the end-point of the titration is approached the pH changes rapidly, and the correct indicator will undergo a sharp color change. The choice of indicator may be readily facilitated by means of Fig. 106 in which the... 

Explain how neutralization reactions are used in acid-base titrations. 

Acid-base titration The stoichiometry of an acid-hase neutralization reaction is the same as that of any other reaction that occurs in solution. In the antacid reaction you just read about, one mole of magnesium hydroxide neutralizes two moles of hydrochloric acid. 

One common laboratory activity, which makes use of the information that we have covered in this chapter, is an acid-base titration reaction. A titration reaction is a neutralization reaction carried out using a solution with a known concentration (called a standard solution), in order to find the concentration of an unknown solution. By determining the volume of the standard solution required to neutralize a specific volume of the unknown solution, we can mathematically determine the concentration of the unknown. An indicator is used to signal the time when neutralization occurs, which is called the end point or the equivalence point of the titration. 

A student carries out an acid-base titration in the laboratory and finds that it takes 4.00 X 102ml of a standard 1.0 M solution of NaOH to neutralize 1.00 x f 02ml of an HC1 solution with an unknown concentration. What would be the concentration of the HC1 solution ... 

A student conducts an acid-base titration laboratory activity and finds that it takes 0.50 L of 4.0 M H2S04 standard solution to completely neutralize 2.0 L of NaOH solution. What is the concentration of the NaOH solution ... 

Demonstration of an acid-base titration that uses the indicator phenolphthalein. An alkaline solution is in the flask, with a few drops of the indicator added to give a purple color. Acid is slowly added from the burette above. When the acid has completely neutralized the alkali in the solution, the indicator turns colorless. This technique is used to gather data for many investigations, such as determining the concentration of the acid or alkali. (Courtesy of Jerry Mason/Science Photo Library)... 

In this chapter we have encountered the most important analytical aspects of acids and bases (a) their individual speciation, as described by the mass action law, and as reflected in the distribution and logarithmic concentration diagrams, (b) their buffer action, and (c) their neutralization, as exploited in acid-base titrations. 

The procednre for the titration is shown in Fignre 4.21. First, a known amount of KHP is transferred to an Erlenmeyer flask and some distilled water is added to make up a solution. Next, NaOH solntion is carefnlly added to the KHP solution from a buret until we reach the equivalence point, that is, the point at which the acid has completely reacted with or been neutralized by the base. The eqnivalence point is usually signaled by a sharp change in the color of an indicator in the acid solution. In acid-base titrations, indicators are substances that have distinctly different colors in acidic and basic media. One commonly nsed indicator is phenolphthalein, which is colorless in acidic and nentral solntions bnt reddish pink in basic solntions. At the equivalence point, all the KHP present has been nentralized by the added NaOH and the solution is still colorless. However, if we add jnst one more drop of NaOH solntion from the buret, the solution will immediately tnm pink becanse the solntion is now basic. Example 4.9 il-Instrates snch a titration. 

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