You need to make a formic acid buffer with a pH of 4.14, and you have a stock so

Question

You need to make a formic acid buffer with a pH of 4.14, and you have a stock solution of 0.682 M formic acid. What concentration (M) of the conjugate base salt, sodium formate, must you use in the buffer? Formic Acid (HCOOH) Ka = 1.8 x 10^-4 Sodium salt = NaHCOO You need to make a formic acid buffer with a pH of 4.14, and you have a stock solution of 0.682 M formic acid. What concentration (M) of the conjugate base salt, sodium formate, must you use in the buffer? Formic Acid (HCOOH) Ka = 1.8 x 10^-4 Sodium salt = NaHCOO You need to make a formic acid buffer with a pH of 4.14, and you have a stock solution of 0.682 M formic acid. What concentration (M) of the conjugate base salt, sodium formate, must you use in the buffer? Formic Acid (HCOOH) Ka = 1.8 x 10^-4 Sodium salt = NaHCOO

Explanation / Answer

apply buffer equation

pH = pKa + log(formate/Formic aicd)

pKa = -log(Ka) = -log(1.8*10^-4) = 3.75

4.14 = 3.75 + log(formate/Formic aicd)

10^(4.14 - 3.75 ) = (formate/Formic aicd)

(formate/Formic acid) = 2.454

if

stock solution = 0.682

(formate/0.682) = 2.454

[formate] = 2.454*0.682 = 1.673628 M of formate

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