Module 7 Chapter 18.1 - 18.5 Acid - Base and Solubility Calculating the pH of a weak acidtitrated with a strong base. An analytical chemist is titrating 228.4mL of a 0.2500M solutionof formic acid (H₂CO₂) with a 0.3900M solution of KOH. The pK of formic acid is 3.74.aCalculate the pH of the acid solution after the chemist has added 162.2mL of the KOHsolution to it. Note for advanced students: you may assume the final volume equals theinitial volume of the solution plus the volume of KOH solution added. Round your answer to2 decimal places.

To calculate the pH of a formic acid solution after titration with KOH, we first determine how much…

Answered: Module 7 Chapter 18.1 - 18.5 Acid -…

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter12: Chemical Equilibrium

Section: Chapter Questions

Problem 12.75PAE: Cyanic acid (HOCN) is a weak acid with AL, = 3.5 X IO-4. Consider the titration of 25.0 inL of 0.125...

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Aniline hydrochloride, (C6H5NH3)Cl, is a weak acid. (Its conjugate base is the weak base aniline, C6H5NH2.) The acid can be titrated with a strong base such as NaOH. C6H5NH3+(aq)+OH(aq)C6H5NH2(aq)+H2O(l) Assume 50.0 mL of 0.100 M aniline hydrochloride is titrated with 0.185 M NaOH. (Ka for aniline hydrochloride is 2.4 105.) (a) What is the pH of the (C6H5NH3) solution before the titration begins? (b) What is the pH at the equivalence point? (c) What is the pH at the halfway point of the titration? (d) Which indicator in Figure 17.11 could be used to detect the equivalence point? (e) Calculate the pH of the solution after adding 10.0, 20.0, and 30.0 mL of base. (f) Combine the information in parts (a), (b), (c), and (e), and plot an approximate titration curve.
A buffer is prepared using the butyric acid/butyrate (HC4H7O2/C4H7O2)acid-base pair. The ratio of acid to base is 2.2 and Ka for butyric acid is1.54105. (a) What is the pH of this buffer? (b) Enough strong base is added to convert 15% of butyric acid to the butyrate ion. What is the pH of the resulting solution? (c) Strong acid is added to the buffer to increase its pH. What must the acid/base ratio be so that the pH increases by exactly one unit (e.g., from 2 to 3) from the answer in (a)?
The titration curves for two acids with the same base are shown on this graph. (a) Which is the curve for the weaker acid? Explain your choice. (b) Give the approximate pH at the equivalence point for the titration of each acid. (c) Explain why the pH at the equivalence point differs for each acid. (d) Explain why the starting pH values of the two acids differ. (e) Which indicator or indicators, phenolphthalein, bromthymol blue, or methyl red, could be used for the titration of Acid 1? For the titration of Acid 2? Explain your choices.
Using Figure 17.11, suggest an indicator to use in each of the following titrations: (a) The weak base pyridine is titrated with HCl. (b) Formic acid is titrated with NaOH. (c) Ethylenediamine, a weak diprotic base, is titrated with HCl. Figure 17.11 Common acid-base indicators. The color changes occur over a range of pH values. Notice that o few indicators hove color changes over two different pH ranges.
Cyanic acid (HOCN) is a weak acid with AL, = 3.5 X IO-4. Consider the titration of 25.0 inL of 0.125 M HOCN with 0.125 M NaOH. Calculate the pH of the solution at each of the following points. Before any NaOH has been added. .After 12.5 mL of NaOH has been added. After 23.0 inL of NaOH has been added. .After 27.0 mL of KOH have been added. Use your calculator or a spreadsheet to plot the titration curve, and use your graph to estimate the pH at the equivalence point.
Consider the nanoscale-level representations for Question 110 of the titration of the aqueous weak acid HX with aqueous NaOH, the titrant. Water molecules and Na+ ions are omitted for clarity. Which diagram corresponds to the situation: After a very small volume of titrant has been added to the initial HX solution? When enough titrant has been added to take the solution just past the equivalence point? Halfway to the equivalence point? At the equivalence point? Nanoscale representations for Question 110.
Malonic acid (HO2CCH2CO2H) is a diprotic acid. In the titration of malonic acid w ith NaOH, stoichiometric points occur at pH = 3.9 and 8.8. A 25.00-mL sample of malonic acid of unknown concentration is titrated with 0.0984 M NaOH, requiring 31.50 mL of the NaOH solution to reach the phenolphthalein end point. Calculate the concentration of the initial malonic acid solution. (Sec Exercise 113.)
A monoprotic organic acid that has a molar mass of 176.1 g/mol is synthesized. Unfortunately, the acid produced is not completely pure. In addition, it is not soluble in water. A chemist weighs a 1.8451-g sample of the impure acid and adds it to 100.0 mL of 0.1050 M NaOH. The acid is soluble in the NaOH solution and reacts to consume most of the NaOH. The amount of excess NaOH is determined by titration: It takes 3.28 mL of 0.0970 M HCl to neutralize the excess NaOH. What is the purity of the original acid, in percent?

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