Question

What is the significance of the formula ${H_2}O$ ?

Answer 1

A chemical formula provides important information on the chemical makeup of any given substance, whether a compound or an element. It names all the elements present in that molecule and the number of atoms of each constituent element of the molecule.

Complete answer:
As we all are familiar with the formula ${H_2}O$ that represents water. This ${H_2}O$ represents one molecule of water. As discussed earlier it also tells us about the atoms which constitute water, which are hydrogen and oxygen. The compound water contains two parts hydrogen to one part oxygen. One can also derive from the formula that hydrogen and oxygen combine in the ratio $1:8$ by mass to form water.
From the given formula we can derive its molecular mass by simply adding the constituent element’s atomic mass. Hydrogen atomic mass is $1$ $amu$ and oxygen atomic mass is $16$ $amu$ , therefore the molecular mass comes to be $18amu$ which equals $18g$ . In terms of moles, a one-mole molecule of water represents $6.022 \times {10^{23}}$ molecules of water.
If we talk about molecular geometry. The oxygen has six valence electrons and needs two more electrons to complete its octet. This then leaves two lone pairs that are not bonded to any other atoms. The two hydrogen atoms and the two lone pairs are as far apart as possible. This lone pair exerts a repulsion on the two bonding hydrogen atoms. This results in ${104^ \circ }$ bond angle.

Note:
There are certain steps one must follow while writing a chemical formula. These include writing the symbols of elements that combine to form the molecule (symbol of metals is written first), the valency of each element, interchanging the valency, etc. also the final formula is written without any sign of charge.