How do you predict products for reactions with acid and base reactants (beyond neutralization reactions), and how do acid base reactions relate to redox reactions?

Question

I'm so sorry--this is such a vague and annoying question. Essentially, as I saw more and more reactions in chemistry, all of the reactions with acids and bases and anhydride acids and bases and acidic and basic oxides and weak acids and bases started confusing me. There seems to be lots of "kinds" of acid base reactions, like combination, hydrolysis, etc, and not just neutralization. There's also redox reactions, which makes a little more sense, but I find it confusing how redox and acid base reactions fit together. All this confusion makes predicting reactants really hard for acid base reactions. Could someone clarify all this for me? I'd appreciate it so so much!!

Answer 1

Arrhenius and Bronsted-Lowry reactions are not ever redox. You'll notice that the oxidation state of any element doesn't change in the reaction. (This is also true for precipitation reactions). Synthesis and decomposition are generally redox unless you have an acid or base anhydride involved (another clue that they are redox is an elemental state moving to or from a reacted state). Single displacement and combustion are always redox. Double displacement is never redox.

Answer 2

I think this is a pretty interesting question with some interesting classifications behind it, which is why there are different classifications of acid and base reactions that could help you predict the reactions due to certain properties

There's Arrhenius acid and bases, which involves explicitly a reaction between H+ and OH-, since Arrhenius acids are defined as chemicals that increase the concentration of H+, so its a molecule that dissociates into H+ and an anion (H+ doesn't really exist, but like in a vacuum kind of like if you have HCl then you can think of H+ as a concept that the original molecule dissociated into it, but H3O+ is what does exist) and Arrhenius bases are defined as chemicals are defined as chemicals that increase the concentration of OH- in solution, so they are molecules that dissociate into a cation and OH-

Then there's Bronsted-Lowry acid and bases, which involves a reaction between chemical species that are proton donors and proton acceptors, respectively. For instance, using NH4+ and converting into NH3 would be an example of a Bronsted-Lowry acid-base reaction, which fit specifically in this classification because the NH4+ isn't dissociating into NH3 and H+ explicitly but instead transfers the proton to H2O. Additionally, NH3 isn't a Arrhenius base because it doesn't dissociate into OH- and all Arrhenius acid and bases are Bronsted Lowry acid and bases.

One last thing about the Bronsted-Lowry definition is that this is the definition that involves the redox reaction being mixed with it, since the definition was made with the intent that acids should react with bases, in the same way that oxidation doesn't occur without reduction, so for instance, in a reaction like NH4+ + H2O -> NH3 + H3O+, NH4+ reacting as a Bronsted-Lowry acid by donating a proton is similar to how a oxidizing agent would help to oxidize in a reaction by losing electrons

The last classification of acid-base reactions is Lewis acid-base reactions, which involve a reaction between an lone pair acceptor and donor, respectively. For example, there's BH3 and would be an example of a Lewis acid because it doesn't donate protons, or increase the concentration of H+, but instead accepts an electron pair from a Lewis base like Cl-, which has lone pairs to donate

So with these different types of acid and bases classifications, you can predict a lot of reactions that could be classified as one of these acid and bases, such as the ones you mentioned

I think one notable example is NH3 and HCl, which you can break down as NH3 accepting a proton to become NH4+ and HCl dissociating into H+ (which is consumed rapidly) and Cl-, which is a Lewis base. Since NH4+ is positively charged and Cl- is negatively charged, they can react again to form an ionic bond with some covalent characterto form the salt NH4Cl