Hi! So, I thought I was very comfortable with distinguishing among Arrhenius, Bronsted-Lowry, and Lewis acids and bases. But then, I answered this question wrong and am looking for help because I'm not sure if my "second choice" answer is correct.
The question asks: In the gas phase reacion below, NH3 is acting as a(n) _______ base but not as a(n) _______ base.
The reaction is illustrated in Lewis structures: NH3 (including the lone electron pair on the N) plus a single hydrogen, H+. Of course, the reaction produces NH4.
At this point, I want to say that NH3 is acting as an Arrhenius base but not a Lewis base. (My initial choice was the exact opposite - I guess not including water threw me off.)
ANY help or clarification would be greatly appreciated!
Arrhenius:
in water solution,
acid = provides H^+
base = provides OH^-
Bronsted-Lowry:
acid = proton donor
base = proton acceptor
Lewis:
acid = electron acceptor
base = electron donor
:NH3 + H^+ ==>NH4^+.
NH3 accepts a proton; therefore, it is acting as a Bronsted-Lowry base.
It is donating a pair of electrons, also, therefore, it is acting as a Lewis base.
No OH^- are involved; therefore, it is not acting as an Arrhenius base.
Thanks, Dr. Bob! It seems my initial thinking was correct. Perhaps the question was marked wrong by mistake!
kjbouho
To determine the correct answer to the question, let's review the definitions of Arrhenius, Bronsted-Lowry, and Lewis acids and bases.
According to the Arrhenius definition, an acid is a substance that produces hydrogen ions (H+) when dissolved in water, while a base is a substance that produces hydroxide ions (OH-) when dissolved in water.
The Bronsted-Lowry definition is more general and defines an acid as a proton (H+) donor and a base as a proton acceptor. In this definition, the reaction can occur in any solvent, not just water.
The Lewis definition is even broader and defines an acid as an electron pair acceptor and a base as an electron pair donor. Lewis acids and bases can react with each other to form coordinate covalent bonds.
Now, let's apply these definitions to the given reaction of NH3 and H+.
In the reaction NH3 + H+ → NH4, NH3 accepts a proton (H+), which fits the Bronsted-Lowry definition. Therefore, NH3 is acting as a Bronsted-Lowry base in this reaction.
Now, let's determine if NH3 is acting as a Lewis base or not. A Lewis base is a substance that donates an electron pair to form a coordinate covalent bond. In the given reaction, NH3 donates its lone pair of electrons to form a bond with H+, which indicates NH3 is also acting as a Lewis base.
So, in conclusion, NH3 is acting as both a Bronsted-Lowry base and a Lewis base in the given gas phase reaction.
I hope this clarifies any confusion you had! If you have any further questions, feel free to ask.