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ACID-BASE Equilibria

  1. Oct 21, 2005 #1
    1.) What is the pH of a buffer solution that is 0.10 NH3 and 0.10 NH4+? What is the pH if 12mL of 0.20 M hydrochloric acid is added to 125 mL of buffer?

    For the first part, i figured that NH3 is the base and NH4+ is the conjugate acid. Therefore, the equil. reaction is NH3 + water --> NH4+ OH-. Using the given concentrations, i found Kb, pOH, and then Ph.

    For the second part, i'm unsure. I figured out the moles of NH3 and NH4+ by multiplying each molarity by 0.125 L. Then i did the same for H3O+ ion (formed by HCl) using 12mL as the volume. However, the problem appears as I'm unsure whether the addition of HCl will depleat the amount of NH4+ or NH3. Should i subtract the moles of the hydronium ion from the moles of NH3 and add it to NH4+? Or the other way around?

    2.) A chloride salt (rantidinium chloride) is presnet in Zantac. Should a solution of rantidinium chloride be acidic, basic, or neutral?

    This is my logic: Since chloride ion forms an acidic solution with Hyrdogen (that is, its a conjugate base of a strong acid), then the solution should be acidic. But i need to consider rantidinium as well, and see whether that is an anion of a strong base, in which case the solution would be neutral. But how do i do that?

    3.) I have to determine whether hydrolysis would occur with the following:

    a.) NO3-
    b.) OCl-
    c.) NH2NH3+
    d.) Br-

    a.) Since NO3- is a conjugate base of a strong acid, no hydrolysis would occur.
    b.) Since OCl- is a conjugate base of a weak acid (HClO), hydrolysis does happen.
    c.) I have no idea!
    d.) Since HBr is a strong acid, no hydrolysis happens.

    My questions are: i.) Why does hydrolysis not happen when an ion is a conjugate acid/base of a strong acid/base? and ii.) Part C.

    Thank you.
  2. jcsd
  3. Oct 24, 2005 #2
  4. Oct 24, 2005 #3


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    Staff: Mentor

    Why do you think you will get here different answer from the one you got at chemicalforums?

    There is one chemistry only ;)
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