How do you write an expression for the acid ionization constant ( $K_a$ ) for $HCHO_2$ ?

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Answer 1 · 2017-03-16T19:07:52

$"For formic acid............?"$

We assess the equilibrium:

$H(O=)COH(l) + H_2O(l) rightleftharpoons H(O=)CO^(-) + H_3O^+$

And we write the equilibrium equation in the usual way:

$K_a="Concentration of products"/"Concentration of reactants"$

$K_a=([H(O=)CO^(-)][H_3O^+])/([H(O=)COH(l)])$ .

This site reports that $K_a$ for formic acid $=1.70xx10^-5$ , so it is a weak Bronsted acid.

How do you write an expression for the acid ionization constant (K_aK_a) for HCHO_2HCHO_2?