4. How much did the pH of water change when NaOH was added? Compare this with thepH change of the buffer when NaOH was added. Look for a change in pH when theNaOH is added. Compare column 3 with columns 4 and 5.5. Why is aspirin sometimes buffered?6. Do research to find how buffers are used in the human body (acid-base homeostasis).Why are buffers important for life? LAB 21Questions for BuffersTable 21.1Row/ColABCD23Solution1Distilleyellowwater3Dated Clear Clear Clear Pink PinkDistilled63Buffer lightpurple2. What is the pH of pure water?4Yellow lightPurple 6Tight,porriea4Buffer Clear Clary clearClear ClearCleary1. How did the pH of the buffer in well D3 compare with the theoretical value of 4.8?5Lab213. How much did the pH of water change when HCI was added? Compare this with the pHchange of the buffer when HCI was added. Look for the change in pH when the HCI isadded, not just the pH. Compare columns 1 and 2 with column 3. Remember that thepH ranges are: bromophenol blue, 3 yellow to 4.6 purple; and phenolphthalein, 8.3 clearto 10 red.

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Table 21.1 Row/Col A Solution 2 5 Distille water Yellow light Pungle Time 3 Distilled Clear Clear Clever Pinks Pink Water 3 6 Buffer light lightie Purple Purple Pujole 4 Buffer Clear Clear y Clear Cleary clear 4 1. How did the pH of the buffer in well D3 compare with the theoretical value of 4.8? B C D 1 yellow 3 3 2. What is the pH of pure water? 4 3. How much did the pH of water change when HCI was added? Compare this with the change of the buffer when HCI was added. Look for the change in pH when the HCli added, not just the pH. Compare columns 1 and 2 with column 3. Remember that th pH ranges are: bromophenol blue, 3 yellow to 4.6 purple; and phenolphthalein, 8.3 c to 10 red.

Table 21.1 Row/Col A Solution 2 5 Distille water Yellow light Pungle Time 3 Distilled Clear Clear Clever Pinks Pink Water 3 6 Buffer light lightie Purple Purple Pujole 4 Buffer Clear Clear y Clear Cleary clear 4 1. How did the pH of the buffer in well D3 compare with the theoretical value of 4.8? B C D 1 yellow 3 3 2. What is the pH of pure water? 4 3. How much did the pH of water change when HCI was added? Compare this with the change of the buffer when HCI was added. Look for the change in pH when the HCli added, not just the pH. Compare columns 1 and 2 with column 3. Remember that th pH ranges are: bromophenol blue, 3 yellow to 4.6 purple; and phenolphthalein, 8.3 c to 10 red.

Chemistry: Principles and Reactions

8th Edition

ISBN:9781305079373

Author:William L. Masterton, Cecile N. Hurley

Publisher:William L. Masterton, Cecile N. Hurley

Chapter14: Equilibria In Acid-base Solutions

Section: Chapter Questions

Problem 54QAP: Ammonia gas is bubbled into 275 mL of water to make an aqueous solution of ammonia. To prepare a...

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Isocyanic acid (HNCO) can be prepared by heating sodium cyanate in the presence of solid oxalic acid according to the equation 2NaOCN(s)+H2C2O4(s)2HNCO(l)+Na2C2O4(s) Upon isolating pure HNCO(l), an aqueous solution of HNCO can be prepared by dissolving the liquid HNCO in water. What is the pH of a l00.-mL solution of HNCO prepared from the reaction of 10.0 g each of NaOCN and H2C2O4, assuming all of the HNCO produced is dissolved in solution? (Ka of HNCO = 1.2 l04.)
Determine the dominant acid-base equilibrium that results when each of the following pairs of solutions is mixed. Indicate the equilibrium by writing 1 for a strong acid, 3 for a weak acid, 4 for an acidic buffer, 7 for a neutral solution, 10 for a basic buffer, 11 for a weak base, and 13 for a strong base. (a) 10.0 mL of 0.15 M NaOH + 15.0 mL of 0.10 M HNO3 (b) 25.0 mL of 0.10 M HCl + 10.0 mL of 0.25 M NH3 (c) 50.0 mL of 0.050 M NaOH + 50.0 mL of 0.10 M NH3 (d) 50.0 mL of 0.10 M NH3 + 50.0 mL of 0.05 M HCl
A buffer is prepared in which the ratio [ H2PO4 ]/[ HPO42 ]is 3.0. (a) What is the pH of this buffer? (b) Enough strong acid is added to convert 15% of HPO42- to H2PO4-. What is the pH of the resulting solution? (c) Enough strong base is added to make the pH 7.00. What is the ratio of [H2PO4-] to [HPO42-] at this point?
A diprotic acid, H2B(MM=126g/moL), is determined to be a hydrate, H2B xH2O. A 10.00-g sample of this hydrate is dissolved in enough water to make 150.0 mL of solution. Twenty-five milliliters of this solution requires 48.5 mL of 0.425 M NaOH to reach the equivalence point. What is x?
Ammonia gas is bubbled into 275 mL of water to make an aqueous solution of ammonia. To prepare a buffer with a pH of 9.56, 15.0 g of NH4Cl are added. How many liters of NH3; at 25C and 0.981 atm should be used to prepare the buffer? Assume no volume changes and ignore the vapor pressure of water.
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.)
What is meant by the capacity of a buffer? Describe a buffer with low capacity and the same buffer with greater capacity.
What is an acidbase indicator? Define the equivalence (stoichiometric) point and the end point of a titration. Why should you choose an indicator so that the two points coincide? Do the pH values of the two points have to be within 0.01 pH unit of each other? Explain.
A good buffer generally contains relatively equal concentrations of weak acid and conjugate base. If you wanted to buffer a solution at pH = 4.00 or pH = 10.00, how would you decide which weak acidconjugate base or weak baseconjugate acid pair to use? The second characteristic of a good buffer is good buffering capacity. What is the capacity of a buffer? How do the following buffers differ in capacity? How do they differ in pH? 0.01 M acetic acid/0.01 M sodium acetate 0.1 M acetic acid/0.1 M sodium acetate 1.0 M acetic acid/1.0 M sodium acetate
The titration of Na2CO3 with HCl bas the following qualitative profile: a. Identify the major species in solution at points AF. b. Calculate the pH at the halfway points to equivalence, B and D. (Hint: Refer to Exercise 113.)
A friend asks the following: Consider a buffered solution made up of the weak acid HA and its salt NaA. If a strong base like NaOH is added, the HA reacts with the OH to form A. Thus the amount of acid (HA) is decreased, and the amount of base (A) is increased. Analogously, adding HCI to the buffered solution forms more of the acid (HA) by reacting with the base (A). Thus how can we claim that a buffered solution resists changes in the pH of the solution? How would you explain buffering to this friend?
Sketch two pH curves, one for the titration of a weak acid with a strong base and one for a strong acid with a strong base. How are they similar? How are they different? Account for the similarities and the differences.