? asked in Science & MathematicsChemistry · 8 years ago

Help me find the pH!? Fast please?

Details PLZ

Update:

The pH of a 0.0250 M solution of sodium benzoate (Kb = 1.6 x 10^-10) is closest to:

1.6

5.7

8.3

11.4

12.4

2 Answers

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  • 8 years ago
    Favorite Answer

    equation:

    pH = ½[ pKw + pKa - log C]

    Ka benzoic acid = 10^-14/(1.6*10^-10) = 6.25*10^-5

    pKa = -log Ka = 4.20

    pH = ½[14 + 4.20 - log 0.0250]

    pH = ½ [ 18.20 - 1.60]

    pH = ½ [ 16.6]

    pH = 8.3

  • 8 years ago

    Bz + H2O <---> HBz + OH-

    Kb = [HBz][OH-]/[Bz-] = 1.6 X 10^-10

    Let x = [HBz] = [OH-]. Then

    x^2 / 0.025 = 1.6 X 10^-10

    x = [OH-] = 2X10^-6

    pOH = 5.7

    pH = 14.0 = pOH = 8.3

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