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Question: A hydrogen electrode placed in a buffer solution of CH3COONa and CH3COOH in the ratios of x : y and ...

A hydrogen electrode placed in a buffer solution of CH3COONa and CH3COOH in the ratios of x : y and y : x has electrode potential values E1 volts and E2 volts, respectively at 25ŗC. The pKa values of acetic acid is (E1 and E2 are oxidation potentials)

A

E1+E20.118\frac{E_{1} + E_{2}}{0.118}

B

E2−E10.118\frac{E_{2} - E_{1}}{0.118}

C

−E1+E20.118- \frac{E_{1} + E_{2}}{0.118}

D

E1−E20.118\frac{E_{1} - E_{2}}{0.118}

Answer

E1+E20.118\frac{E_{1} + E_{2}}{0.118}

Explanation

Solution

E1 =−0.0591log⁡[H+]\frac{- 0.059}{1}\log{}\left\lbrack H^{+} \right\rbrackor

pH1 = E1 / 0.059 = pKa + log xy\frac{x}{y} pH2 = E2 / 0.059

= pKa + log xy\frac{x}{y} or E1+E20.059=2pKaorpKa=E1+E20.118\frac{E_{1} + E_{2}}{0.059} = 2pK_{a} or pK_{a} = \frac{E_{1} + E_{2}}{0.118}