Chemistry: The Molecular Nature of Matter and Change 7th Edition

Published by McGraw-Hill Education
ISBN 10: 007351117X
ISBN 13: 978-0-07351-117-7

Chapter 19 - Problems: 19.9

Answer

See explanation below.

Work Step by Step

1. (a) Add 0.1 M NaOH to the buffer NaOH is a strong base, the added OH- will react with HA to produce NaA. As a result, the ratio of NaA to HA will increase. Hence, Buffer component ratio will increase. ...... (Ans 1) When OH- reacts with HA, the HA will get consumed, thus reducing the acid concentration of the solution. Hence, on adding O.1 M NaOH, the pH will increase. ...... (Ans 2) 2. (b) Add 0.1 M HCl to the buffer HCl is a strong acid, the added H+ will react with NaA to produce HA. As a result, the ratio of NaA to HA will decrease. Hence, Buffer component ratio will decrease. ...... (Ans 1) When H+ reacts with HA, the base A- will get consumed, thus reducing the base concentration of the solution. Hence, on adding O.1 M NaOH, the pH of buffer will decrease. ...... (Ans 2) 3. (c) Dissolve pure NaA in the buffer On adding NaA to the buffer, the concentration of A-, will increase, thereby increasing the ratio of NaA to HA. Also, as A- is a base, the overall base concentration of the buffer will increase, thereby increasing the pH of the solution. Hence, buffer component as well as pH will increase. 4. (d) Dissolve pure HA in the buffer On adding HA to the buffer, the concentration of H-, will increase, thereby decreasing the ratio of NaA to HA. Also, as HA is an acid, the overall acid concentration of the buffer will increase, thereby decreasing the pH of the solution. Hence, buffer component as well as pH will decrease.
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