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Is the pH actually only 1 if I dissolve 1mol of HCl in 1l of Water?


Hey guys,

I'm currently learning about acids and bases and their potency. I'm doing a presentation thereof and I want to use the hypothetical example of dissolving 1mol of hydrogen chloride in 1 liter of water. I have to work out the pH of the resulting solution. As HCl is a strong acid, my calculation is as follows:

pH = -log(c(HCl)), where c(HCl) = 1mol/l
Which solves to
pH = 0

However, I've never seen a solution with a pH of 0 so I am very skeptical of my result. I would be super delighted if anyone of you could confirm or falsify my result.

Thank you very much, I appreciate it!

Best wishes, Marc :D

why would you think a pH = 0 is questionable?

pH is defined as
  pH = -log[H+]
  [H+] = 10(-pH)
so if pH = 0
  [H+] = 100 = 1
all you need for pH=0 is a 1M concentration of H+ ions (or H3O+)

likewise pH's can be - for concentrated mineral acids such as HCl, H2SO4, etc. 

Thank you very much. I knew that water is neutral at a pH of seven due to autoprotolysis and I just assumed that this autoprotolysis limited the pH physically to be between 0 and 14. I didn't have a rational explanation to this though but I didn't realize that this was a wrong assumption beforehand. Thanks for clearing this up for me, have a nice one!

Pure water only sometimes shows pH=7 - at 25°C


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