Question

Is nitric acid the strongest acid and acetic acid the weakest?

Answer 1

Far from it!

Explanation:

The strongest acid

Probably the strongest common acid is perchloric acid, `"HClO"_4 ("p"K_text(a) = "-10")`.

It is `10^7` times as strong as sulfuric acid, `"H"_2"SO"_4 ("p"K_text(a) = "-3")` which, in turn, is 50 times stronger than nitric acid, `"HNO"_3 ("p"K_text(a) = "-1.3")`.

However, the strongest acid known is fluoroantimonic acid, `"H"_2"SbF"_6`. Its Hammett acidity function, `H_0 = "-31.3"`. This makes it more than `10^19` times as strong as sulfuric acid.

The weakest acid

The weakest common acid is probably `"HCN" color(white)(l)("p"K_text(a) = 9.2)`.

Acetic acid (`"p"K_"a" = 4.8`) is 25 000 times stronger than `"HCN"`.

However, the weakest acids are probably the alkanes (`"p"K_"a" ≈ 50`)

The weakest acid is probably cyclopentane. Its Bordwell `"p"K_"a" = 59`.

Even ethylene (`"p"K_"a" = 50`) is a billion times more acidic than cyclopentane.