Lewis Acids and Bases

[abby hyman]

Hi can someone explain to me what it means that the acid donates protons to the base?

[Akshata Kapadne 2K]

You are actually referring to Brønsted acids and bases, not Lewis. When a Brønsted acid donates protons to a base, this means that it is donating an H⁺ ion to the base. For example, in the equation HCl+NH₃→NH₄⁺+Cl^-, HCl is a Brønsted acid because it donates its H+ ion to NH3. Once it loses its H+, it becomes Cl-. On the other hand, NH₃ is a Brønsted base because it accepts a proton (H+), so it becomes NH₄⁺. I hope this helps!

[Kiara Phillips 3L]

To add to what Akshata mentioned, I think it is also important to note that when a Brønsted acid dissociates, it increases the concentration of H+ ions in the solution; conversely, Brønsted bases dissociate by taking a proton Fromm the solvent (water) to generate [OH-]. It is also important to understand the concept of conjugate acids and bases as well as the concept polyphonic acids and bases. Hope this helps!

[Saumya Tawakley 1E]

Based on lectures, it seems like a Lewis base will donate an electron pair to a Lewis acid which will accept that electron pair. Generally Lewis bases are negatively charged (since they have an electron pair to donate) and Lewis acids are positively charged (since they have yet to accept an electron pair). A good example is with BF4-, where BF3 accepts an electron pair from F- to form BF4-.