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    I have four problems that I don't understand how to figure out. I've done problems 16-20 but don't know how to do 21-24.
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    Given 100 mL of the H2C6H8O6/NaHC6H8O6 buffer you just made, answer the following questions about the effect of a challenge to your buffer when 1.0 mL of 1.2 M HCl (stomach acid) is added to that buffer.

    21. After the challenge with HCl, the pH of your buffered solutoin is
    22. After the challenge with HCl, the moles of HCl remaining in your buffer is
    23. After the challenge with HCl, the acidity of your buffered solution is
    24. After the challenge with HCl, the final H+ concentration of your buffered solution is

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    The facts: Molarity of C6H8O6 is 0.02 M
    Molarity of NaC6H7O6 is 0.04 M

    So in 100 ml buffer solution, the moles of C6H8O6 is (100 ml)(0.02 M) = 2 mmol
    The moles of NaC6H7O6 is (100 ml)(0.04 M) = 4 mmol

    The moles of HCl added is (1 ml)(1.2 M) = 1.2 mmol
    We can ignore the change in the volume of the solution, that is, the final volume is still 100 ml after HCl is added.

    The reaction of NaC6H7O6¬ with HCl
    NaC6H7O6 + HCl NaCl + C6H8O6
    Initial 4 1.2 2
    Change -1.2 -1.2 +1.2 +1.2
    Final 2.8 0 1.2 3.2
    HCl is only 1.2 mmol, so it is the limiting reactant. All HCl reacts with NaC6H7O6 to produce C6H8O6.

    After HCl is added, the moles of NaC6H7O6 is 4 - 1.2 = 2.8 mmol
    The moles of C6H8O6 is 2 + 1.2 = 3.2 mmol

    The molarity of NaC6H7O6 is 2.8 mmol / 100 ml = 0.028 M
    The molarity of C6H8O6 is 3.2 mmol / 100 ml = 0.012 M

    So the answer to 19 is 3.2 mmol or 0.0032 mol. Answer is A.
    Answer to 20 is 0.0028 mol. Answer is D

    21. It is the same as No. 14.
    The pH of the buffer solution is

    Answer: C

    22. E

    23. The H+ concentration after HCl challenge is
    The original H+ concentration in the buffer is (pH = 4.4, see No. 14)
    So the acidity increases by
    Answer: D

    24.

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

    © BrainMass Inc. brainmass.com October 3, 2022, 11:40 pm ad1c9bdddf>
    https://brainmass.com/chemistry/acids-and-bases/buffer-solution-challenged-hcl-215697

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