[AngelShare]

Problem: Complete Table 1 by noting how each theory defines acids and bases. Also, list chemical reactions that demonstrate the action of each acid or base. For example, in the reaction HA --> H⁺ + A^-, HA acts as an Arrhenius acid.

Firstly, I'd like to check my answers for the chemical reactions part.

Arrhenius:

Acids- HA --> H⁺ + A^-
Bases- XOH --> X⁺ + OH^-

Bronsted-Lowry:

Acids- ?
Bases- ?

This is all that was listed:

HCl + H₂O <===> H₃O⁺ + Cl^-

HNO₃ + H₂O <===> H₃O⁺ + NO₃^-

HC₂H₃O₂ + H₂O <===> H₃O⁺ + C₂H₃O₂^-

NH₃ + H₂O <===> NH₄⁺ + OH^-

I don't really understand them though...

Lewis:

Acids- HNO₃ => H⁺¹ + NO₃^-1
Bases- ?

To be honest, I don't really understand what I'm doing. I started reading what I was assigned but I got stuck on Bronsted-Lowry's theory so I took out the book my public school loaned me. Since this is a new chapter, I started off reading the basics and worked my way up to the three theories mentioned on my lesson page. Doing so only manged to confuse me more because now I'm wondering where the "A" and "X" are coming from in my first answer.

Maybe someone could explain this to me or give me some sites?

[mrdeadman]

arrhenius-can act as an acid or a base, water is an example
"A" is the conjugate base and "X" is the conjugate acid.
Bronsted-lowry: acid-electron pair acceptor, base-electron pair donor.
Lewis: acid-proton donor, base-proton acceptor

[AngelShare]

Defining each one isn't the problem, the second part ("list chemical reactions that demonstrate the action of each acid or base") is where I'm stuck. I don't really understand those equations or if they're right... I'm not really sure what's got me stuck either because I started reading at the beginning.

[xiankai]

HCl + H₂O <===> H₃O⁺ + Cl^-

HNO₃ + H₂O <===> H₃O⁺ + NO₃^-

HC₂H₃O₂ + H₂O <===> H₃O⁺ + C₂H₃O₂^-

NH₃ + H₂O <===> NH₄⁺ + OH^-

based on your definitions for arrhenius acid/bases, u can seperate each reagent into H+ and A-, or X+ and OH-, where A- is an anion and X+ is a cation.

then on the products side, u match up the cations and anions that have been formed

[Will]

arrhenius-can act as an acid or a base, water is an example
"A" is the conjugate base and "X" is the conjugate acid.
Bronsted-lowry: acid-electron pair acceptor, base-electron pair donor.
Lewis: acid-proton donor, base-proton acceptor

I was taught:
Arrhenius- acid: increases conc. of H₃O⁺_(aq). base: increases conc. of OH^-_(aq)
Brønsted-Lowry- acid: proton donor. base: proton acceptor.
Lewis- acid: electron pair acceptor. base: electron pair donor.

AngelShare, all your equations are correct. Which bit of them don't you understand? Why its an equilibrium, why they lose/gain protons?
The A and the X are just used to represent the rest of the molecule, so A could equal -Cl, so HA would be HCl and A^- (Cl^-) is formed when HCl dissociates in water (A could also be -OSO₃H, -ONO₂, -OCOCH₃ etc.). In the same way, X can be used to represent something like Na, so when NaOH dissociates in water, X⁺ (Na⁺) is formed (X can also be K etc.).
I would rather use the equations HA + H₂O --> H₃O⁺ + A^- for acids and X + H₂O --> XH⁺ + OH^- (or something along those lines) for bases (that way X can represent NH₃, C₅H₅N etc.).

[mrdeadman]

hmmm, maybe i got the lewis and brontsed-lowry backwards then.

[AngelShare]

Alright, now that I've pulled my public school's book out, I'm a bit more on track. I'm stuck though...

Which of the three theories is applicable to the greatest number of acids and bases? Explain your reasoning.

My public school's textbook doesn't mention Lewis's theory. It seems to focus quite a bit on Brønsted-Lowry's theory so I'm assuming that means Lewis's isn't the best of the three? If so, that'd leave Brønsted-Lowry because it seems to fill in the holes left open by Arrhenius's.

[AngelShare]

hmmm, maybe i got the lewis and brontsed-lowry backwards then.

My textbook says...

Arrhenius Acid: a substance that dissociates in water to produce hydrogen ions
Arrhenius Base: a substance that dissociates in water to produce hydroxide ions

Brønsted-Lowry Acid: any substance that can donate H+ ions
Brønsted-Lowry: any substance that can accept H+ ions

[xiankai]

Lewis' is the best of the three, because it involves the donation and acceptance of electron pairs. now since all atoms/molecules/elements/compounds/acids/bases bla bla bla have electron pairs, u know...

[Will]

Lewis' is the best of the three, because it involves the donation and acceptance of electron pairs. now since all atoms/molecules/elements/compounds/acids/bases bla bla bla have electron pairs, u know...

I would agree with xiankai, but personally I would rather use the Brønsted-Lowry definition, mostly because H⁺ ions are easier to think about than electron pairs!
"The Lewis definition is one of the most broad definitions and is necessary for an understanding of acid-base reactions, although the Brønsted-Lowry definition is sufficient and more practical for most cases in everyday use."

[rctrackstar2007]

Lewis' is the best of the three, because it involves the donation and acceptance of electron pairs. now since all atoms/molecules/elements/compounds/acids/bases bla bla bla have electron pairs, u know...

I would agree with xiankai, but personally I would rather use the Brønsted-Lowry definition, mostly because H⁺ ions are easier to think about than electron pairs!
"The Lewis definition is one of the most broad definitions and is necessary for an understanding of acid-base reactions, although the Brønsted-Lowry definition is sufficient and more practical for most cases in everyday use."

i totally agree with this one

the bronstead-lowery definition is more simple to work with plus i've never really had to deal with lewis acid-base cuz a lot of things only share that H+ ion