pH calculation without calculator

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or just use the power of number as the maximum it could be.

If it is 1 x 10 ^-10 then pH is 10. If it is 2 x 10^-10 then it's probably 9.8 or so. 6 x 10^-10 would be 9.3 or so etc.
 
Here's how I do it.

Suppose H+= 6*10^-3. This is greater than 1*10^-3 (which has a pH of 3) but less than 1*10^-2 (a pH of 2). also look for the number in between: 2.5, which has a pH of 3.16*10^-3 (always 3.16*10^ pH rounded up...so 6.5 would have 3.16*10^-7)

Your answer will be in between 2 of these values.

When given a pH and you need H+:

say pH= 6.6
This is between 6 (1*10^-6 H+) and 7 (1*10^-7 H+). But also check the middle one! (6.5= 3.16*10^-7 H+)
Your H+ will fall in between two of these.

And this also works for OH/pOH!!

Hope this helps!
 
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