Question

What is the formula for potassium hydroxide?

Answer 1

Hint: Chemical formula for any compound represents the total number of atoms present in that molecule. The chemical formula is written in such a way that cation, which is a positive species, is written first and then the anion, which is the negative species is written after. Potassium hydroxide contains potassium and hydroxide (OH) atoms.

Complete answer:
A chemical formula for any compound is the representation of the total number of atoms involved in a molecule. While writing the chemical formula for any molecule, IUPAC has suggested a rule that the cation is named and written before the anion of that molecule. The cation is the ion that contains a positive charge, while anion carries the negative charge.
We have been given potassium hydroxide. This compound consists of potassium and hydroxide (OH) as the atoms. The potassium ion is represented as, ${{K}^{+}}$, as it is a metal that has 1 electron in the outer shell which gets donated. While the hydroxide ion is represented as, $O{{H}^{-}}$ as hydroxide gains 1 electron to complete its octet, potassium has a charge of positive of 1 while hydroxide has a charge of negative of 1. The chemical formulas of compounds are written in such a manner, as to compensate the valencies or charges present in the atoms of the element. For instance, one positive charge containing ions cannot form a compound with an element having a charge of negative two. Therefore, those positive ions are taken in a quantity of two, as to compensate the valence of the negative ions. So, an ion with a charge of +1 will form a molecule with an ion of charge of -1.
Thus, potassium (K) and hydroxide (OH) both contain a charge of +1 and -1, which means they are taken in a quantity of 1. So, their formula becomes KOH.
Hence, the formula for potassium hydroxide is KOH.

Note:
Potassium is a highly reactive metal as it has only 1 electron in its valence shell, and is placed in group 1, so it has a group oxidation state of +1 and readily donates 1 electron. While, hydroxide is a molecule containing hydrogen and oxygen that require 1 electron to complete their octet in the molecule.