Question

What is an Arrhenius base?
A) Species that increases the concentration of ${H^ + }$ ions.
B) Species that increase the concentration of $O{H^ - }$ions.
C) Species that increases the concentration of both ${H^ + }$and $O{H^ - }$ions.
D) None of these

Answer 1

We need to remember that It is easy to identify a base and an acid. A base usually contains a hydroxide ion. For example:$NaOH$, $KOH$. Whereas, an acid contains ${H^ + }$ ions in it. For example: $HCl$, ${H_2}S{O_4}$.

Complete answer:
Option A) this is an incorrect option as the species that increases the concentration of ${H^ + }$ions is termed as Arrhenius acid.
We can understand this by looking at this example:
On making an aqueous solution of $HCl$, it dissociates itself into ${H^ + }$ and $C{l^ - }$ ions.
$HCl \to {H^ + } + C{l^ - }$
As the concentration of ${H^ + }$ increases in the solution, thus $HCl$ is an Arrhenius acid.
Option B) this is a correct option as the species that increases the concentration of $O{H^ - }$ ions is termed as Arrhenius base.
We can have a look at an example to understand this well.
In water $KOH$ fully dissociates in water to give ${K^ + }$ and $O{H^ - }$ ions.
$KOH \to {K^ + } + O{H^ - }$
As the concentration of $O{H^ - }$ (hydroxide ion) increases in the solution, thus $KOH$ is an Arrhenius base.
So this is a correct option that defines Arrhenius base.
Option C) this is an incorrect option, as both Arrhenius base and Arrhenius acid reacts together to form water and a salt.
For example:
$HF + LiOH \to {H_2}O + LiF$
Option D) this is an incorrect option.

So we get Option B as a correct answer.

Note:
Sometimes, when an Arrhenius base reacts with an Arrhenius acid the products so formed are water and a salt, this type of reaction may be called a Neutralization reaction. Also, Arrhenius theory is limited to acid-base chemistry only.