Question

What is a substance that is an acid under the Bronsted-Lowry model, but not under the Arrhenius model?

Answer 1

how is acid defined in each of the models?

Answer 2

The Arrhenius model defines an acid as a substance that produces hydrogen ions when dissolved in water, and the Bronsted-Lowry model defines an acid as any species that provides hydrogen ions in a reaction.

Answer 3

your bronsted-lowry definition is wrong, an acid is a proton (H+) donor.. so whats a substance in a reaction that donates a proton but does not produce hydronium ions in solution?

Answer 4

Would NH4+ work?

Answer 5

yep

Answer 6

thanks!

Answer 7

no prob!

Answer 8

That's not right. NH4+, e.g. in NH4Cl, is an Arrhenius acid, because it releases H+ on dissolution. The fact that it requires a reaction with H2O isn't relevant, because almost all releases of H+ on dissolution require that.

It's actually trickier to think of BL acids that aren't Arrhenius acids than in the case of bases (e.g. NH3 is a BL base but not an Arrhenius base). The easiest case off the top of my head are metal cations, which are Lewis acids but definitely not Arrhenius acids, e.g. Al+3 does this:\[{\rm Al}^{3+}(aq) + 3 {\rm H}_2{\rm O}(l) \rightarrow {\rm Al}{\rm (OH)}_3(aq) + 3 {\rm H}^{+}(aq)\]The metal cation is here producing H+ not be releasing it itself, but by ripping an OH- off from waters.

Answer 9

umm what if you had: NH4Cl + OH- -> H2O + NH3 + Cl-

Answer 10

What about it? What's the difference from HCl + OH- -> H2O + Cl-?