Sodium hydroxide titration with acetic acid

Titration profile of acetic acid (CH3COOH) with sodium hydroxide (NaOH). Maximum buffering capacity is at pH = pK, at which point minimal change in pH occurs upon addition of acid or base. 

Titration reaction (the acetic and hydrochloric acids are titrated with sodium hydroxide). 

The substance is hydrolysed by boiling under reflux with 50 per cent sulphuric acid and the acetic acid or benzoic acid produced is distilled in steam and titrated with sodium hydroxide solution, using phenolphthalein as indicator. 

The titration curve for 100 mL of 0.1 M acetic acid titrated with 0.1 M sodium hydroxide is shown in Figure 8.5. The neutralization reaction is... 

The amount of the acetic acid released is determined by titration with sodium hydroxide, which makes it possible to determine the amount of hydrogen ions taking part in the hydrolytic reaction. 

Calculate the relative amounts of acetic acid and acetate ion present at the following points when 1 mol of acetic acid is titrated with sodium hydroxide. Also use the Henderson-Hasselhalch equation to calculate the values of the pH at these points. Compare your results with Figure 2.13. 

The acetic-acid content of household vinegar can be determined by potentiometric titration with sodium hydroxide. Mixtures of carbonate and bicarbonate can be analyzed by titration with HCl. 

Benzoic acid and its salts may be determined by titration with sodium hydroxide after extraction of the benzoic acid from an aqueous food suspension into chloroform, and evaporation of the chloroform and any acetic acid present (AOAC method 963.19). Vanillin interferes with this determination and a more selective method involves the determination of benzoic acid in an ether extract by UV absorption at 272 nm, as described in AOAC method 960.38. An alternative method of isolating benzoic acid from food involves the use of steam distillation and TLC separation. These sample preparation techniques are used in AOAC method 967.15 prior to the determination of benzoic acid by UV absorption. 

Fatty acids do not show a great variation in their acidities, as indicated by their pKaS. Nonanoic acid, for example, has a pKa of 4.96, being only slightly weaker than acetic acid (4.76). As the chain length increases the solubility of the fatty acids in water decreases very rapidly, so that the longer-chain fatty acids have minimal effect on the pH of an aqueous solution. Even those fatty acids that are insoluble in water will dissolve in warm ethanol, and can be titrated with sodium hydroxide solution using phenolphthalein... 

A typical weak acid-strong base titration is that of acetic acid with sodium hydroxide. The net ionic equation for the reaction is... 

Weak acid with a strong base. In the titration of a weak acid with a strong base, the shape of the curve will depend upon the concentration and the dissociation constant Ka of the acid. Thus in the neutralisation of acetic acid (Ka— 1.8 x 10-5) with sodium hydroxide solution, the salt (sodium acetate) which is formed during the first part of the titration tends to repress the ionisation of the acetic acid still present so that its conductance decreases. The rising salt concentration will, however, tend to produce an increase in conductance. In consequence of these opposing influences the titration curves may have minima, the position of which will depend upon the concentration and upon the strength of the weak acid. As the titration proceeds, a somewhat indefinite break will occur at the end point, and the graph will become linear after all the acid has been neutralised. Some curves for acetic acid-sodium hydroxide titrations are shown in Fig. 13.2(h) clearly it is not possible to fix an accurate end point. 

Weak acids with weak bases. The titration of a weak acid and a weak base can be readily carried out, and frequently it is preferable to employ this procedure rather than use a strong base. Curve (c) in Fig. 13.2 is the titration curve of 0.003 M acetic acid with 0.0973 M aqueous ammonia solution. The neutralisation curve up to the equivalence point is similar to that obtained with sodium hydroxide solution, since both sodium and ammonium acetates are strong electrolytes after the equivalence point an excess of aqueous ammonia solution has little effect upon the conductance, as its dissociation is depressed by the ammonium salt present in the solution. The advantages over the use of strong alkali are that the end point is easier to detect, and in dilute solution the influence of carbon dioxide may be neglected. 

To select an indicator for an acid-base titration it is necessary to know the pH of the end point before using equation (5.5) or standard indicator tables. The end point pH may be calculated using equations (3.27), (3.29) or (3.30). Alternatively, an experimentally determined titration curve may be used (see next section). As an example, consider the titration of acetic acid (0.1 mol dm 3), a weak acid, with sodium hydroxide (0.1 mol dm-3), a strong base. At the end point, a solution of sodium acetate (0.05 mol dm 3) is obtained. Equation (3.28) then yields... 

Suggest suitable colour change indicators for the titration of (a) acetic acid (0.100 M) with sodium hydroxide (0.100 M) and (b) nitric acid (0.0100 M) with sodium hydroxide (0.0100 M). Give the reasons for your choice. 

In the process of a weak acid or weak base neutralization titration, a mixture of a conjugate acid-base pair exists in the reaction flask in the time period of the experiment leading up to the inflection point. For example, during the titration of acetic acid with sodium hydroxide, a mixture of acetic acid and acetate ion exists in the reaction flask prior to the inflection point. In that portion of the titration curve, the pH of the solution does not change appreciably, even upon the addition of more sodium hydroxide. Thus this solution is a buffer solution, as we defined it at the beginning of this section. 

Titration of acetic acid with sodium hydroxide pH versus ml of NaOH. 

The amount of hydroxyl group present is found by titrating the resulting acetic acid (CH3COOH) with standard sodium hydroxide, as in (1). 

In general, the aliphatic hydroxyl content of a lignin preparation is determined by subtraction of the phenolic hydroxyl content (see Chap. 7.2) from the total hydroxyl content of the lignin. The total hydroxyl content of lignin (partial structure H) can be determined by acetylation with acetic anhydride-pyridine reagent (10) followed by saponification of the acetate (partial structure 12) and titration of the resulting acetic acid (14) with a standard 0.05 N sodium hydroxide solution (Roth 1953). 

The a-naphthol is dissolved as described for j3-naphthol, and the solution is diluted and then precipitated with dilute acetic acid in the presence of 25 cc. 25 per cent sodium acetate solution. The coupling is carried out as with -naphthol, except that when the reaction for o-naphthol disappears, the solution is made alkaline with sodium hydroxide, reprecipitated with acetic acid, and the titration continued until the a-naphthol reaction again disappears. Frequently, as much as 30 per cent of the total volume of the diazonium solution is added in the second part of the titration, since so much of the naphthol is carried down by the dye. 

The reaction between aspirin and gastric acid may be followed by titrating the liberated salicylic and acetic acids with sodium hydroxide. In an experiment using equimolar amounts of reactants, the following data were obtained ... 

Figure 14-5 Curve for the titration of acetic acid with sodium hydroxide. Curve A 0.1000 M acid with 0.1000 M base. Curve B 0.001000 M acid with 0.001000 M ba.se.

The second and third columns of Table 14-3 contain pH data for the titration of 0.1000 M and 0.001000 M acetic acid with sodium hydroxide solutions of the same two concentrations. In calculating the values for the more dilute acid, none of the approximations shown in Example 14-3 were valid, and solution of a quadratic equation was necessary until after the equivalence point. In the postequivalence point region, the excess OH predominates, and the simple calculation suffices. 

H20(1) + NaC2H302(aq) You win titrate several brands of commercial vinegar with sodium hydroxide solution of a known concentration, and use your data to calculate the molarities and volume percentages of acetic acid in the vinegars. 

Fig. 4. The Titration of Sodium Hydroxide with 0.11 Normal Acetic Acid.

Fig. 6. The Titration of Acetic Acid, at Different Dilutions, with Sodium Hydroxide.

Fig. 7. The Titration of a Mixture of 0.01 Normal Hydrochloric Acid and 0.01 Normal Acetic Acid with Sodium Hydroxide.

The reaction must be stoichiometric. That is, there must be a well-defined and known reaction between the analyte and the titrant. In the titration of acetic acid in vinegar with sodium hydroxide, for example, a well-defined reaction takes place ... 

What would be a suitable indicator for the titration of ammonia with hydrochloric acid Of acetic acid with sodium hydroxide ... 

Sodium cyanate, a reagent with a short shelf life, requiring frequent titration, has been used in cold, dilute acetic acid to convert o-aminoamides to 2-ureidobenzamides (155), which can be cyclized to quinazoline-2,4-diones (see 1) by heating at 100°C with 7 N hydrochloric acid, 8 N sodium hydroxide,257 or simply in water.258 No yields were published. Ammonium thiocyanate, similarly acidified, was used to convert 2-aminothiophene-3-carboxamide to 2-thioxothieno[2,3-d]pyrimidin-4-ones (see 12).255... 

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