Kw usage

[Garmani Kyaw]

In some problems we can use molar concentration of acid times molar concentration of base to get 10^-14. For example, if we want to know M of acids we can divide 10^14 by the M of base.

But in questions like 6B.9, dividing 10^-14 by M of an base wont give you the correct M of acid.

When do we know if Kw is not 10^-14

[Jeffrey Doeve 2I]

Kw is an equilibrium constant for the autoprotolysis of water. As a result, it is temperature dependent. The value of 1*10^-14 for Kw is only valid when the temperature is 25 C. Otherwise, you would have a different Kw to use in calculations at temperatures other than 25 C.

[ellenulitsky Dis 1I]

I believe that if the temperature is not 25 degrees Celsius then the Kw is not 10^-14. Hope this helps!

[Rohit Srinivas 2D]

I believe for 6B.9 you do still use the kw of 10^-14.

[sophia kosturos 2B]

Kw=10^-14 is the equilibrium constant for the autoprotolysis of water, which means that it is temperature-dependent and is only true at 25 degrees celsius. If the reaction is not present at. 25 degrees celsius then this Kw value is no longer valid and cannot be used to find the correct M.

[305572629]

It is safe to assume that the Kw value will = 10^-14 in all equilibrium systems at 25 degrees Celsius.

[Nishan Reddy 3K]

Sometimes the Kw value changes at different temperatures since the rate autoionization of water changes at different temperature. Thus, you must make sure to use the correct value in order to get the correct value.