5. At 20°C, the water autoionization constant, Kw, is 6.8 ´ 10–15. What is the H3O+ concentration in neutral water at this temperature? A. 6.8 × 10–7 M B. 3.4 × 10–15 M C. 6.8 × 10–15 M D. 8.2 × 10–8 M E. 1.0 × 10–7 M

Respuesta :

Explanation:

Let us assume that the concentration of [[tex]OH^{-}[/tex] and [tex]H^{+}[/tex] is equal to x. Then expression for [tex]K_{w}[/tex] for the given reaction is as follows.

          [tex]K_{w} = [OH^{-}][H^{+}][/tex]

          [tex]K_{w} = x^{2}[/tex]

      [tex]6.8 \times 10^{-15} = x^{2}[/tex]

Now, we will take square root on both the sides as follows.

          [tex]\sqrt{6.8 \times 10^{-15}} = \sqrt{x^{2}}[/tex]

          [tex][H^{+}] = 8.2 \times 10^{-8}[/tex] M

Thus, we can conclude that the [tex]H_{3}O^{+}[/tex] concentration in neutral water at this temperature is [tex]8.2 \times 10^{-8}[/tex] M.

Answer: The concentration of [tex]H_3O^+[/tex] in neutral water is [tex]8.2\times 10^{-8}M[/tex]

Explanation:

The chemical equation for the ionization of water follows:

[tex]2H_2O\rightleftharpoons H_3O^++OH^-[/tex]

The expression of [tex]K_w[/tex] for above equation, we get:

[tex]K_w=[H_3O^+]\times [OH^-][/tex]

We are given:

[tex]K_w=6.8\times 10^{-15}[/tex]

[tex][H^+]=[OH^-]=x[/tex]

Putting values in above equation, we get:  

[tex]6.8\times 10^{-15}=x\times x\\\\x=8.2\times 10^{-8}M[/tex]

Hence, the concentration of [tex]H_3O^+[/tex] in neutral water is [tex]8.2\times 10^{-8}M[/tex]