[yasas.w]

Lets say there's an HCl solution in 30°C and its pH=2
If the same solution is kept in an environment of 25°C what happenes to the pH value?

[billnotgatez]

There are lots of places on the internet that discuss this
here is one of them
http://www.chembuddy.com/?left=pH-calculation&right=water-ion-product
It has a table showing  pH variation with temperature where pH of 7 is 25C

Also you should discuss your work on the question - not just ask a question
Please read forum rules

[yasas.w]

There are lots of places on the internet that discuss this
here is one of them
http://www.chembuddy.com/?left=pH-calculation&right=water-ion-product
It has a table showing pH with temperature

its about the neutral temperature which means it doesn't solve my question 

[billnotgatez]

I am sorry but I modified my post after you answered my post
But if you read the text in the link it says

In a real world Kw value is highly temperature dependent

You can also look at WIKI
http://en.wikipedia.org/wiki/PH
for discussions on calculations

And as yet we have not seen your work on this question
Have you read the forum rules?

[yasas.w]

I am sorry but I modified my post after you answered my post
But if you read the text in the link it says

In a real world Kw value is highly temperature dependent

You can also look at WIKI
http://en.wikipedia.org/wiki/PH
for discussions on calculations

And as yet we have not seen your work on this question
Have you read the forum rules?

sorry I just read them =)
Well the original question is(I'm translating it into English forgive me if there are any mistakes)
"In a HCl solution pH=2, temperature is 30°C.
What is the pOH value if you keep the same solution in an environment of 25°
(In 25°C pKw=14)"

And I thought that pH doesn't depend on the temperature and I thought that the answer should be 12 

Well I know what happens to Kw with the variations of the temperature but I was wondering whether the temperature really affects the pH value of the HCl solution.

[Borek]

Changes in pH value are most likely neglectable.

Doesn't mean they don't exist, but they are quite difficult to describe, as there are several competing phenomena present.