# What is a Bronsted-Lowry acid?

Aug 8, 2018

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#### Explanation:

A $\text{Bronsted-Lowry acid}$ is a species that DONATES a proton in the form of an hydrogen ion...

$2 {H}_{2} O \left(l\right) r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} + H {O}^{-}$

And, here, water molecules has acted as a $\text{Bronsted-Lowry acid}$ AND as a $\text{Bronsted-Lowry BASE}$, a proton acceptor...

Of course in water under standard conditions, the given equilibrium is measurable...

i.e. ${K}_{w} = \left[H {O}^{-}\right] \left[{H}_{3} {O}^{+}\right] = {10}^{- 14}$...

And taking logs of both sides...

$- {\log}_{10}^{- 14} = {\log}_{10} \left[{H}_{3} {O}^{+}\right] + {\log}_{10} \left[H {O}^{-}\right]$

And so...

$+ {\log}_{10}^{- 14} = {\underbrace{- {\log}_{10} \left[{H}_{3} {O}^{+}\right] - {\log}_{10} \left[H {O}^{-}\right]}}_{p H + p O H = 14}$

And you will use this relationship a lot...

$14 = p H + p O H$...