2 of 14 Another student is investigating the change in pH during a titration where sodium hydroxide solution is added from a burette into a beaker containing propanoic acid. The pH curve produced during this titration is shown below: 14 13 Volume of NaOH added (cm³) d. Explain how a pH curve like the one above can be used to deduce the value of Ka for a weak acid. 210으9876543210 537.5 40 42.5 45 47.5 52.5 55

2 of 14 Another student is investigating the change in pH during a titration where sodium hydroxide solution is added from a burette into a beaker containing propanoic acid. The pH curve produced during this titration is shown below: 14 13 Volume of NaOH added (cm³) d. Explain how a pH curve like the one above can be used to deduce the value of Ka for a weak acid. 210으9876543210 537.5 40 42.5 45 47.5 52.5 55

Fundamentals Of Analytical Chemistry

9th Edition

ISBN:9781285640686

Author:Skoog

Publisher:Skoog

Chapter15: Complex Acid/base Systems

Section: Chapter Questions

Problem 15.29QAP

See similar textbooks

Similar questions

Figure 15-3 outlines the classic scheme for separating a mixture of insoluble chloride salts from one another. Explain the chemistry involved in the various steps of the figure.
Given three acid-base indicatorsâ€”methyl orange (end point at pH 4), bromthymol blue (end point at pH 7), and phenolphthalein (end point at pH 9)â€”which would you select for the following acid-base titrations? (a) perchloric acid with an aqueous solution of ammonia (b) nitrous acid with lithium hydroxide (c) hydrobromic acid with strontium hydroxide (d) sodium fluoride with nitric acid
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.)
acetic acid, CH3COOH is a commercially weak acid with a value of Ka = 1.8 x 10 ^ -5. In an erlenmeyer, you titrate 50 mL of this acid with 0.103 M NaOH and the phenolphtalein indicator duplo. The volume of NaOH needed to reach the equivalence point in both experiments was 48.96 mL and 49.11 mL. a. Write down the equilibrium reaction of dissolving vinegar in water, then write down the equation that reflects the acidic equilibrium constant!b. Calculate the average volume of NaOH needed to reach the equivalence point!c. Calculate the acidity of the vinegar in this sample!d. Calculate the initial pH of the vinegar solution before titrating!e. Calculate the pH at the equivalence point
Many chemical reactions are carried out in the presence of buffers. Use the Henderson-Hasselbalch equation to provide a recommendation for a suitable acete/acetic acid buffer under the following reaction conditions. a) If a checial reaction produces hydroxide ion, OH-, what would be the range for the target pH of a buffer soution that would favor pH stabilizatoin under these conditions? Explain.
2. You are studying an unusual enzyme that produces hydronium ions (H3O+) during the courseof the reaction.You wish to maintain pH = 8.5 for the enzyme-catalyzed reaction. Which weak acid will serveas the better 0.1 M buffer for the reaction: HEPPS with pKa = 8.0, or, AMPSO with pKa = 9.0?Justify your answer by describing how the buffer “resists” change in pH and the chemical logicof why you chose the buffer you did.
a student was titrating a solutin of acitic acid with a sodium hydroxid solution. determin the ph at the equivilance point. do this by constructing a bca table, constructing and ice table, writing the equlibrium constant expresion and find the ph. the ka for ch3cooh is 1.8e-5. a 50ml solutin of 0.3 m of ch3cooh was titrated with 0.3 m of naoh.
Many chemical reactions are carried out in the presence of buffers. Use the Henderson-Hasselbalch equation to provide a recommendation for a suitable acete/acetic acid buffer under the following reaction conditions. a) If a checial reaction produces hydroxide ion, H3O+, what would be the range for the target pH of a buffer soution that would favor pH stabilizatoin under these conditions? Explain.
A sufficient quantity of each of the following aqueous solutions has been made available to you: (i) 0.2M NaH2PO4; (ii) 0.1M Na2HPO4 (a) How many ml of each of these two solutions would you require to mix together in order to prepare one litre of a 0.01M phosphate buffer pH 7.2? [For H3PO4: pKa1 = 2.15; pKa2 = 6.82; pKa3 = 12.38]. (Ans. = 14.7 ml 0.2M NaH2PO4; and 70.6 ml Na2HPO4). (b) Having calculated these volumes (of 0.2 M NaH2PO4 and 0.1M Na2HPO4) required, what further steps would you take to prepare the 0.01M phosphate buffer solution of pH 7.2?
One drop, 0.200 cm3, of 1.00 mol dm-3 of aqueous sodium hydroxide, NaOH, solution is added to 25.0 cm3 of a phosphate buffer that is 0.040 mol dm-3 in KH2PO4(aq) and 0.020 mol dm-3 in K2HPO4(aq). Calculate the resulting pH of the solution given that the second acid dissociation constant, pKa2, for phosphoric acid is 7.21.
A buffer is prepared using lactic acid (HLac) and sodium lactate (NaLac). 0.300 dm3 of the 0.500 mol·dm–3 HLac solution is mixed with 0.300 dm3 of the 0.300 mol·dm–3 NaLac solution to prepare the buffer. Ka for lactic acid (HLac) is 1.4 x 10-4 a) Calculate the pH of the lactic acid before it is mixed with the NaLac to form the buffer. b) Calculate the pH of the sodium lactate solution before it is mixed with the HLac to form the buffer. c) Calculate the pH of the buffer solution.
Explain why the indicator cresol red changes color when the pH is lowered from 10 to 6. What colors will be observed at pH 10, 8, and 6? Why does the color transition require ,2 pH units for completion?