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Hc2h3o2(aq)+h2o(l)⇌h3o+(aq)+c2h3o−2(aq) kc=1.8×10−5 at 25∘c part a if a solution initially contains 0.260 m hc2h3o2, what is the equilibrium concentration of h3o+ at 25∘c? express your answer using two significant figures.

Respuesta :

Answer : The equilibrium concentration of [tex]H_3O^+[/tex] at [tex]25^oC[/tex] is, [tex]2.154\times 10^{-3}m[/tex].

Solution : Given,

Equilibrium constant, [tex]K_c=1.8\times 10^{-5}[/tex]

Initial concentration of [tex]HC_2H_3O_2[/tex] = 0.260 m

Let, the 'x' mol/L of [tex]H_3O^+[/tex] are formed and at same time 'x' mol/L of [tex]HC_2H_3O_2[/tex] are also formed.

The equilibrium reaction is,

                  [tex]HC_2H_3O_2(aq)+H_2O(l)\rightleftharpoons H_3O^+(aq)+C_2H_3O_2^-(aq)[/tex]

Initially                0.260 m                       0                 0

At equilibrium    (0.260 - x)                     x                 x

The expression for equilibrium constant for a given reaction is,

[tex]K_c=\frac{[H_3O^+][C_2H_3O_2^-]}{[HC_2H_3O_2]}[/tex]

Now put all the given values in this expression, we get

[tex]1.8\times 10^{-5}=\frac{(x)(x)}{(0.260-x)}[/tex]

By rearranging the terms, we get the value of 'x'.

[tex]x=2.154\times 10^{-3}m[/tex]

Therefore, the equilibrium concentration of [tex]H_3O^+[/tex] at [tex]25^oC[/tex] is, [tex]2.154\times 10^{-3}m[/tex].

A solution of CH₃COOH (Ka  = 1.8 × 10⁻⁵) with an initial concentration of CH₃COOH of 0.260 M has an equilibrium concentration of H₃O⁺ at 25 °C of 2.16 × 10⁻³ M.

Let's consider the reaction for the ionization of CH₃COOH.

CH₃COOH(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CH₃COO⁻(aq)

The acid ionization constant (Ka) is 1.8 × 10⁻⁵ and the initial concentration of acetic acid (Ca) is 0.260 M.

For a weak monoprotic acid, we can calculate the equilibrium concentration of H₃O⁺ at 25 °C using the following expression.

[tex][H_3O^{+} ] = \sqrt{Ca \times Ka } = \sqrt{(0.260) \times (1.8 \times 10^{-5} ) } = 2.16 \times 10^{-3} M[/tex]

A solution of CH₃COOH (Ka  = 1.8 × 10⁻⁵) with an initial concentration of CH₃COOH of 0.260 M has an equilibrium concentration of H₃O⁺ at 25 °C of 2.16 × 10⁻³ M.

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