Question

Please answer the following questions regarding the nature of buffers:

Part 1: A few drops of 1.0 M HCl are added to pure water and to a buffered solution containing hydrogen phosphate (HPO42-) and dihydrogen phosphate (H2PO4-). You observed that the pH of the pure water drops significantly, while the pH of the buffered solution only decreases slightly. Which explains the result?

A) H2PO4- reacted with the HCl, changing to HPO42- and removing H+ from solution

B) HPO42- reacted with the HCl, changing to H2PO4- and removing H+ from solution

C) H2PO4- reacted with the HCl, changing to H3PO4 and removing H+ from solution

Part 2: A few drops of 1.0 M NaOHl are added to pure water and to a buffered solution containing hydrogen phosphate (HPO42-) and dihydrogen phosphate (H2PO4-). You observed that the pH of the pure water increases significantly, while the pH of the buffered solution only increases slightly. Which explains the result?

A) HPO42- reacted with the NaOH, changing to H2PO4- and removing OH- from solution

B) HPO42- reacted with the NaOH, changing to PO43- and removing OH- from solution

C) H2PO4- reacted with the NaOH, changing to HPO42- and removing OH- from solution

Part 3: You begin with 43 mL of the buffered solution. If the solution is 1.0 M H2PO4- and 0.5 M HPO42-, how many mL of the 1.0 M solution of HCl would be needed to 'overwhelm' and completely react with the buffer?

Part 4: You begin with 43 mL of the buffered solution. If the solution is 1.0 M H2PO4- and 0.5 M HPO42-, how many mL of the 1.0 M solution of NaOH would be needed to 'overwhelm' and completely react with the buffer?

Part 5: Buffers are solutions that can accept protons in the presence of a base and donate protons in the presence of an acid. Which of these would be able to function as a buffer?

A) Weak Acid + Weak Base

B) Weak Acid + Strong Acid

C) Weak Base + Strong Base

D) Strong Acid + Strong Base

Part 6: Buffers are defined as a solution containing one of the following:

1)A weak acid and that weak acid’s conjugate base

2)A weak base and that weak base’s conjugate acid Which of the following solutions would form a buffer? Select all that apply.

A) NH3 + NH4+

B) HF + F-

C) NH3 + NaOH

D) HF + HCl

E) OH- + H+