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A 230.0 −mL buffer solution initially contains 2.0×10−2 M of HCHO2 and 2.0×10−2 M of NaCHO2....

A 230.0 −mL buffer solution initially contains 2.0×10−2 M of HCHO2 and 2.0×10−2 M of NaCHO2. What mass of the correct reagent should you add?

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Expert Solution

HCHO2      =     H^+    +    CHO2^-

I(M)    2*10^-2            0              2*10^-2

C(M)         -x                 + x                + x

           -----------------------------------------

As the pH is 4.10, [H+] = 10^-4.10   =   7.94*10^-5 M

                       so, x = 7.94*10^-5 M

Hence equilibrium concentration is  7.94*10^-5 M

    Moles =   7.94*10^-5 M * 0.230 L = 1.8262*10^-5 mol

Mass of reagent = 1.8262*10^-5 mol x 40.00 = 0.00073 g

queen_honey_blossom answered 2 years ago
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