name a compound that acts as a weak base?
methanol?
define the term weak bronsted-lowry base
im not sure how to put this in words, but a weak base is found when you got a strong acid, when your ka is high, kb will be low.
I take issue with some of the definitions of strong acids/strong bases I have seen at this site. By definition, strong acids and strong bases, Bronsted-Lowry or otherwise) are those that ionize 100% and that usually means in aqueous solution. Here is a good site to read about all of that.
http://www.chemguide.co.uk/physical/acidbaseeqia/acids.html
A compound that acts as a weak base is methanol.
To understand the term "weak Brønsted-Lowry base," let's break it down. The Brønsted-Lowry theory defines an acid as a substance that donates a proton (H+) and a base as a substance that accepts a proton.
A weak base is a substance that accepts protons less readily, meaning it has a lower tendency to gain a proton compared to a strong base. The strength of a base is determined by its equilibrium constant for the reaction of the base accepting a proton, known as the base dissociation constant or Kb. A weak base will have a relatively low Kb value, indicating a lower proportion of the base will dissociate to accept protons. This is in contrast to a strong base with a higher Kb value, where a larger proportion of the base will readily accept protons.
In relation to your mention of ka and kb, it's important to note that the acid dissociation constant (Ka) and the base dissociation constant (Kb) are related as follows:
Ka x Kb = Kw
Kw is the equilibrium constant for the self-ionization of water. Since water is a solvent in many acid-base reactions, it dissociates into hydronium ions (H3O+) and hydroxide ions (OH-). In an aqueous solution, Kw has a constant value (1.0 x 10^-14) at a given temperature.
Therefore, if you have a strong acid (which has a high Ka value, indicating a high proportion of the acid will donate protons), then its conjugate base will be a weak base (with a low Kb value, indicating a low proportion of the base will accept protons). This phenomenon is known as the acid-base conjugate relationship.
I hope this explanation clarifies the concept of a weak Brønsted-Lowry base for you!