I don't get pH... Why is it the -log(H+)?

Question

rane · Answer

you really dont get it?

anonymous · Answer

Nope.

anonymous · Answer

If you do care to explain ;D

abb0t · Answer

What is not to get? Lol
To find a concentration from a pH, we use the formula: $[H_3O^+]= 10^{-pH}$
to find the pH, you take the log of both sides, you get: $log(H_3O^+)=-pH$, but you don't want the negative on the pH side, so you multiply both sides by -1, and you get: $-log(H_3O^+)=pH \Rightarrow pH = -log(H_3O^+)$

aaronq · Answer

$$pH=\log\frac{ 1 }{ a _{H _{3}O ^{+}} }$$

pH is the logarithm of the reciprocal of the activity (not concentration) of the hydronium ion concentration

we use concentration because it's often a good estimate

$$pH=\log \frac{ 1 }{ [H _{3}O ^{+}] }$$

using logarithm laws we write it as:

$$pH=-\log[H _{3}O ^{+}]$$

anonymous · Answer

So that's just how it is then... I guess this is my first time learning it to yeah. Thanks for the insight @aaronq and @abb0t.