Bases Titration weak

A slrang acid-weak base titration. The curve represents Ihe titration of 50.00 mL of 1.000 M ammonia, a weak base, with 1.000 M HCI. The solution at the equivalence point is acidic because of the NfV ion. Methyl red is a suitable indicator phenolphthalein would change color much too early. 

Why do you suppose we ignore weak acid-weak base titrations ... 

Cation of a weak base titrated with a strong base. The pH at the stoichiometric end point is given by ... 

TABLE 11.2 Summary of Weak Acid and Weak Base titration Equilibria... 

Example demonstrates that at the stoichiometric point in any weak base titration, the pH is less than 7.0. 

For some very weak bases, titration in water is not feasible. Using appropriate equations, explain why this would be the case for aniline, C6H5NH2, which has a ffb of 4.6 X 10-10. 

In this section, you examined acid-base titration curves for combinations of strong and weak acids and bases. You may have noticed the absence of a curve for the reaction of a weak acid with a weak base. A weak acid-weak base titration curve is difficult to describe quantitatively, because it has competing equilibria. You may learn about this curve in future chemistry courses. 

O <2ZD In a titration, a basic solution is added to an acidic solution, and measurements of pH are taken. Compare a strong acid-strong base titration and a strong acid-weak base titration in terms of... 

Weak base titrated with H B + H+ — BH+ (Ve = equivalence volume)... 

Acid-base Various questions about strong acid/weak base titration... 

There are a few main types of titrations a strong acid titrated with a strong base (or a strong base titrated with a strong acid) a weak acid titrated with a strong base a weak base titrated with a strong acid and a polyprotic acid titrated with a strong base. Each one of these produces characteristic results and will need to be discussed separately. For the solutions of weak acids and bases, the process is complicated by the common-ion effect. 

Of considerable difference with the titrations of weak acids and weak bases are the buffering effects of the conjugate salts. The titration curves (see Figure 14.6) all contain a buffering region near the equivalence point where most of the solution consists of the conjugate base (for a weak acid titration a conjugate acid for a weak base titration). 

Solubility profile of a weak base (titration regime)... 

TLie pH at tlie equivaLence point of an acid-base titration depends on liydroiysis of the salt formed in the neutraiization reaction. For strong acid-strong base titrations, the pH at the equivaLence point is 7 for weak acid-strong base titrations, the pH at the equivalence point is greater than 7 for strong acid-weak base titrations, the pH at the equivalence point is less than 7. 

The curve for a weak acid/weak base titration is the composite of the curves for a weak acid/ strong base and weak base/strong acid titrations, as indicated (Figure 6.5). 

Weak Acid/Weak Base Titration Curves... 

Understand how an acid-base indicator works, how the equivalence point and end point in an acid-base titration differ, and how strong acid-strong base, weak acid-strong base, and strong acid-weak base titration curves differ explain the significance of the... 

Sketch the titration curve for a weak base titrated by a strong acid. Weak base-strong acid titration problems also follow a two-step procedure. What reaction takes place in the stoichiometry part of the problem What is assumed about this reaction At the various points in your titration curve, list the major species present after the strong acid (HNO3, for example) reacts to completion with the weak base, B. What equilibrium problem would you solve at the various points in your titration curve to calculate the pH Why is pH < 7.0 at the equivalence point of a weak base-strong acid titration If pH = 6.0 at the halfway point to... 

The calculation of values along a weak acid/weak base titration curve (other than the initial pH and the equivalence point) is beyond the scope of this text. 

Figure 19-6 Thetitratlon curve for 100. mLof O.IOOMCH3COOH with 0.100 M aqueous NH3. At the equivalence point for this weak acid/weak base titration, the pH is 7.0, but this is not true for all such combinations (see Section 18-10). Because the solution is buffered before and after the equivalence point, the pH changes very gradually near the equivalence point. Color indicators cannot be used in such titrations. Instead, physical methods such as conductivity measurements or pH electrode-based instruments can be used to detect the end point.

Titrate with SDS in acid and alkaline solution, or with NaTPB at pH 3 and 10 or 13. The weak base titrates in the acid but not in the alkaline medium. 

---