Methylamine (CH3NH2) forms hydroxide ions in aqueous solution. Why is methylamine a Brønsted-Lowry base but not an Arrhenius base?
I need help on this question. Please explain this to me!
The old definition of an Arrhenius base was that the substance contained hydroxide ion.Under that definition CH3NH2 is not a base because it doesn't contain OH ions. However, the definition has been modified to make it fit more modern times. Frankly, I consider CH3NH2 an Arrhenius base, too, because the modified definition of an Arrhenius base is one that produces OH^- in solution and CH3NH2 does just that.
http://en.wikipedia.org/wiki/Acid%E2%80%93base_reaction
Why was methylamine never invited to the Arrhenius base party? Because it didn't fit the definition, silly!
But see, here's the deal: Arrhenius bases are substances that dissociate in water to produce OH- ions, right? Well, methylamine doesn't quite fit that criteria. It's not like methylamine breaks apart and throws OH- ions into the water like a wild party animal.
However, it’s still considered a Brønsted-Lowry base. Brønsted-Lowry bases are defined as substances that accept protons (H+ ions). In the case of methylamine, it's capable of accepting a proton from water to form the methylammonium ion (CH3NH3+), and this lovely little ion can then behave as an Arrhenius acid by donating a proton to water, forming hydronium ions (H3O+).
So, in short, methylamine didn't RSVP to the Arrhenius base party, but it's totally cool hanging out with the Brønsted-Lowry crowd!
Methylamine (CH3NH2) is indeed a Brønsted-Lowry base but not an Arrhenius base. To understand this, we need to first understand the definitions of these two types of bases.
1. Arrhenius base: According to Arrhenius theory, a base is a substance that releases hydroxide ions (OH-) in aqueous solution. This definition only applies to solutions that contain water.
2. Brønsted-Lowry base: According to Brønsted-Lowry theory, a base is a substance that accepts a proton (H+) in a chemical reaction. This definition applies to both aqueous and non-aqueous solutions.
Now, let's discuss why methylamine is considered a Brønsted-Lowry base but not an Arrhenius base:
Methylamine (CH3NH2) is a weak base that readily accepts a proton (H+). In an aqueous solution, methylamine can react with water molecules, acting as a base by accepting a proton from water molecules.
Methylamine + H2O ⟶ CH3NH3+ + OH-
In this reaction, methylamine accepts a proton (H+) from water, forming a methylammonium ion (CH3NH3+) and hydroxide ion (OH-). Therefore, methylamine exhibits Brønsted-Lowry base behavior in aqueous solution.
However, methylamine does not dissociate into hydroxide ions (OH-) in water, which is the characteristic of an Arrhenius base. Since methylamine does not release hydroxide ions into the solution, it is not defined as an Arrhenius base.
To summarize, methylamine is considered a Brønsted-Lowry base because it can accept a proton in a chemical reaction. However, it is not an Arrhenius base because it does not dissociate into hydroxide ions in aqueous solution.
To understand why methylamine (CH3NH2) is considered a Brønsted-Lowry base but not an Arrhenius base, let's first define what these terms mean:
- Brønsted-Lowry base: According to the Brønsted-Lowry theory, a base is a substance that can accept a proton (H+) from another substance by donating an electron pair. In other words, a base is a proton acceptor.
- Arrhenius base: According to the Arrhenius theory, a base is a substance that produces hydroxide ions (OH-) when dissolved in water.
Now let's analyze why methylamine falls under the Brønsted-Lowry definition of a base but not the Arrhenius definition:
1. Brønsted-Lowry base: Methylamine acts as a base because it can accept a proton (H+) from another substance by donating an electron pair. In the case of methylamine, the lone pair of electrons on the nitrogen atom can accept a proton, forming the methylammonium cation (CH3NH3+).
CH3NH2 + H+ → CH3NH3+
Here, the nitrogen atom in methylamine acts as the proton acceptor, making it a Brønsted-Lowry base.
2. Arrhenius base: An Arrhenius base is a substance that produces hydroxide ions (OH-) when dissolved in water. However, methylamine does not dissociate into hydroxide ions when dissolved in water. Instead, it undergoes partial ionization to form the methylammonium cation and forms a solvated hydroxide ion from water.
CH3NH2 + H2O ⇌ CH3NH3+ + OH-
In this case, although a hydroxide ion is formed, it is not directly produced by the dissociation of methylamine. Instead, it is produced due to the solvation of the amine with water molecules.
Therefore, methylamine is considered a Brønsted-Lowry base because it can accept a proton, but it is not classified as an Arrhenius base since it does not dissociate to produce hydroxide ions directly in water.