Question

Which of the following alkali metal hydroxides is the strongest base?
${\text{A}}{\text{. LiOH}}$
${\text{B}}{\text{. KOH}}$
${\text{C}}{\text{. NaOH}}$
${\text{D}}{\text{. RbOH}}$

Answer 1

Hint: The property of the element depends upon the number of electrons present in its valence shell. In the given question we will look after this property of each element for finding out the stable metal once $O{H^ - }$ is removed.

Complete step-by-step answer:
Hydroxide is a chemical compound containing one or more groups consisting of one atom which is bound together by oxygen and hydrogen and acts as the negative charged $O{H^ - }$ ion. The compound's positively charged component is typically a metal ion. It can also be an organic group.
When we break the positive and negative ions of each compound then we get
${\text{LiOH}} \to {\text{L}}{{\text{i}}^ + } + {\text{ O}}{{\text{H}}^ - }$
${\text{KOH}} \to {K^ + } + {\text{ O}}{{\text{H}}^ - }$
${\text{NaOH}} \to N{a^ + } + {\text{ O}}{{\text{H}}^ - }$
${\text{RbOH}} \to R{b^ + } + {\text{ O}}{{\text{H}}^ - }$
The strongest base will be the compound in which the metal ion is formed by donating $O{H^ - }$ ions in the most stable form.
Hence the stability of positive ions can be arranged as
$L{i^ + } \to N{a^ + } \to {K^ + } \to R{b^ + }$
Hence we can see that $L{i^ + }$ is the most stable ion and hence we can say ${\text{LiOH}}$ is the strongest base.
Therefore, option A is the correct answer and as per this ${\text{LiOH}}$ is the strongest base.

Note: For answering these types of questions we must remember the periodic table and the positions of elements in that. We can see that the elements are arranged in the periodic table based on that atomic number and it is dependent on the number of electrons in the valence shell.