Why is the concentration of [OH-] not equal to the square root of Kw?

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The discussion centers on calculating the hydroxide ion concentration, [OH-], using the ion product of water, Kw, at 50°C, which is given as 5.48 x 10^-14. The initial assumption is that taking the square root of Kw would yield the correct [OH-] concentration, resulting in 2.34 x 10^-7. However, the conversation reveals confusion regarding whether additional context or information is needed for the calculation. It is clarified that for pure water, where [H+] equals [OH-], the formula [OH-] = √Kw is valid. The participants emphasize that the definition of Kw as Kw = [H+][OH-] supports this approach, confirming that the calculation is correct under the assumption of pure water at the specified temperature.
disneychannel
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So I thought if I have the value of Kw and I need to find the concentration of [OH-] then all I would have to do is square root the Kw. But in this example, it is not the case why?

Kw at 50oC is 5.48x10-14. Calculate OH- concentration

so i just square rooted 5.48x10-14 and got 2.34 x10-7. Shouldn't this be right?
 
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For a pure water at 50°C that would be a correct approach. Is there some additional information in the question?
 
No. It just states "calculate the [OH] concentration from the above solution at 50 degrees" But, I am pretty sure that would not make a difference. Correct?
 
disneychannel said:
No. It just states "calculate the [OH] concentration from the above solution at 50 degrees" But, I am pretty sure that would not make a difference. Correct?

What is "the above solution"?
 
Kw= [H+][OH-] by definition.
If [H+]=[OH-] then [OH-]=Sqrt (Kw)
 

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