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What is the molarity of 555 l of a ba(oh)2 solution if the ph is 10.20? 1. 2.26 × 10−5 m 2. 6.31 × 10−11 m 3. 5.15 × 10−7 m 4. 3.15 × 10−11 m 5. 3.14 × 10−4 m 6. 1.58 × 10−4 m 7. 7.92 × 10−5 m 8. 4.40 × 10−2 m?

Respuesta :

superman1987
First, you need to get POH from the value of PH:

when POH = 14 - PH 

                   = 14 - 10.2

                    = 3.8
then we are going to get the value of [OH] from the POH value:

POH = -㏒[OH-]

3.8  = - ㏒ [OH-]

∴[OH-] = 1.58 x 10^-4

then, we will get the moles of ba(OH)2 = (1.58 x 10^-4) / 2 

                                                                  = 0.0000792 moles 

∴ the molarity of Ba(OH)2 = 7.92 x 10^-5
sebassandin

Answer:

7. 7.92 × 10−5

Explanation:

Hello,

In this case, with the given pH, one could find the pOH:

[tex]pOH=14-pH=14-10.20=3.8[/tex]

Thus, since barium hydroxide is completely dissolved in water based on:

[tex]Ba(OH)_2\rightarrow Ba^{+2}+2OH^-[/tex]

The concentration of hydroxyl ions is twice to that of the hydroxide (2:1 mole relationship). Therefore, by considering the relationship between the pOH and the concentration of hydroxyl we have:

[tex]pOH=-log([OH]^-)\\[/tex]

[tex][OH]^-=10^{-3.8}=1.58x10^{-4}M[/tex]

Finally, given the 1:2 mole ratio of barium hydroxide to hydroxyl ions, the concentration of barium hydroxide results:

[tex][Ba(OH)_2]=2*[OH^-]=\frac{1}{2} *1.58x10^{-4}M[/tex]

[tex][Ba(OH)_2]=7.92x10^{-5}M[/tex]

Thus, the answer is 7. 7.92 × 10−5.

Regards.

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