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rosie
rosie asked in Science & MathematicsChemistry · 11 months ago

What is the pH of this buffer solution?

A buffer solution is made when 1.50 g of sodium hydroxide are added to 1.00 dm3 of a 0.150 mol dm–3 solution of a weak acid HA.

For HA, the acid dissociation constant, Ka = 1.79 × 10−5 mol dm−3.

Calculate the pH of this buffer solution.

1 Answer

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  • hcbiochem
    Lv 7
    11 months ago
    Favorite Answer

    Ka = 1.79X10^-5 = [H+][A-]/[HA]

    Initial moles HA = 0.150 mol

    moles NaOH added = 1.50 g / 40.0 g/mol = 0.0375 mol

    The NaOH quantitatively neutralizes HA forming A-. So, after the addition, 

    moles A- = 0.0375

    moles HA = 0.150 - 0.0375 = 0.1125

    1.79X10^-5 = [H+](0.0375)/(0.1125)

    [H+] = 5.37X10^-5

    pH = 4.270

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