Question

Given `1*mol*L^-1` concentrations of `"hydrochloric, acetic, and formic acids"` in water, can you rank the solutions in order of INCREASING `pH`?

Answer 1

`pH=-log_10[H_3O^+]`; `pH` follows the order `HCl` `<` `HCO_2H` `<` `H_3C-CO_2H` with respect to `1` `mol*L^-1` concentrations of these acids.

Explanation:

And thus the STRONGEST acid will generate the LOWEST, i.e. the most negative `pH`. The given order is wrong.

`HCl` completely dissociates to give `pH=-1`. Formic acid should be a stronger acid than acetic acid, and will thus have a more negative `pH`; you will look up the `pK_a` values to verify what I say.