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Confused about pH!!!?
Okay, so can someone please explain why pH doesn't depend on volume? If pH=-log of the concentration of H+, then why would the pH in the following example simply be the -log of the given concentration, ignoring the volume?
So if we have 50mL of 0.1M HCl, the pH is 1, since pH=-log(0.1)
Why wouldn't it be -log(0.005)=2.30? For every other calculation in chemistry involving concentration/moles (and even in acid base chemistry when you combine acids and bases, for that matter), the volume is important because it tells us how many moles are actually present.
So in this case, why is the volume irrelevant?
1 Answer
- NikhileshLv 78 years agoFavorite Answer
Answer
The concentration expressed as 0.1 M HCl means 0.1 moles HCl / lit. A concentration of 0.1 moles / lit HCl , if all of it dissociates to H+, then we get 1 mole/ lit H+
[H+] = 0.1
-log(0.1) = 1.26
pH = 1.26
The volume of the solution therefore does not figure in the calculation. When concn is in moles / lit, it does not matter if the volume of the soln is x or y
