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Calculate the pH of:
a) ammonia, 0.1M, in water
b) ammonium chloride, 0.1M, in water
c) a buffer solution containing ammonia (0.1M)and ammonium chloride (0.01M)

For NH4^+, pKa = 9.25

  • Chemistry -

    NH3 + H2O ==> NH4 + OH^-

    Kb = (NH4^+)(OH^-)/(NH3)

    (NH4^+) = y
    (OH^-) = y
    (NH3) = 0.1 - y
    Plug into Kb and solve for y.

    b) NH4Cl + HOH ==> NH4^+ + Cl^-
    The NH4^+ hydrolyzes as follows:
    NH4^+ + H2O ==> NH3 + H3O^+
    Ka = Kw/Kb = (NH3)(H3O^+)/(NH4^+)
    (NH3) = y
    (H3O^+) = y
    (NH3) = 0.1 - y
    solve for y.

    c) Use the Henderson-Hasselbalch equation.

    Post your work if you get stuck on any of these.

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