pH changes

20 ml of sodium hydroxide (pH = 14) is reacted with 20 ml of hydrochloric acid (pH = 1).

What is the final pH and why?

Possible answers:

14, something between 7 and 14, 7, something between 7 and 1, 1, "need more information".

Think carefully and logically. There is more to this than you think!

Clue for answers

Many people think (wrongly) that pH is a scale from 1 - 14. They would guess that equal amounts of each extreme would lead to th middle "avergae" value.....WRONG!

Calculate the moles of H+and OH- present and then see what is left over.......

 Can't work out the moles of H+and OH-? Think of the definition of pH (pH = -log10[H+]) ...

....and use Kw = [H+][OH-]

More clues later if you need them.

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