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Calculate the pKa of hypochlorous acid (HClO, a weak acid). A 0.015 M solution of hypochlorous acid has a pH of 4.64.

Sagot :

Answer:

"7.46" is the correct answer.

Explanation:

Given that:

[tex]pH=4.64[/tex]

[tex]C=0.015 \ M[/tex]

The equation:

⇒ [tex]HA \rightleftharpoons H^++A^-[/tex]

HA = C - Cα

H⁺ = Cα

A⁻ = Cα

now,

⇒ [tex]pH=-log(H^+)[/tex]

          [tex]=-log(C \alpha)[/tex]

          [tex]=4.64[/tex]

    [tex]C \alpha = 2.3\times 10^-5 \ M[/tex]

As we know,

⇒ [tex]K_a=C \alpha^2[/tex]

         [tex]=(\frac{C \alpha}{C} )^2\times C[/tex]

         [tex]=\frac{(2.3\times 10^{-5})^2}{0.015}[/tex]

         [tex]=3.5\times 10^{-8}[/tex]

hence,

⇒ [tex]pK_a=-log(K_a)[/tex]

           [tex]=7.46[/tex]