Whats the 5% rule in chemistry?

Question

make it so i understand

Answer 1

the 5% rule is used for pH calculation

calculating the pH is pretty tricky; it depends on temperature, for instance, so it's very hard to get it right

this rule is based on the fact that: pH = -log[H+]

so we do not need to get the exact number of [H+]. instead, being wrong by 5% is fine (=> 95% - 105%)

you can prove this by calculating the pH of an acid with [H+] 0.0001 M, and calculate the pH of either (0.000095 or 0.000105)

the difference is insignificant