Question

What is the formula for dihydrogen monoxide?

Answer 1

Hint : Dihydrogen monoxide, most commonly known as water, is a transparent fluid forming the world's streams, oceans, lakes and rain, and is actually the major component of the fluid of organisms. A molecule of water is a chemical compound containing one oxygen atom and two hydrogen atoms which are connected through covalent bonds.

Complete Step By Step Answer:
As the name suggests, the given compound dihydrogen monoxide comprises a non-metal hydrogen and another non-metal oxygen. We know that any compound containing a non-metal and another non-metal is considered to be a covalent compound (most commonly known as molecular compound). Now let us identify the formula for the given molecular compound i.e. dihydrogen monoxide. Rules for writing the formula of a molecular compound are listed below:

1. Write the symbol for each of the elements according to their appearance in the periodic table.
   In the present case, the symbol for hydrogen is $H$ and the symbol for oxygen is $O$ in accordance with the periodic table.
2. Add a subscript to each of the elements according to its prefix. The examples of the subscript corresponding to its prefix are listed below:

Prefix	Subscript
Mono-	1
di-	2
Tri-	3
Tetra-	4
Penta-	5
Hexa-	6
Hepta-	7
Octa-	8
Nona-	9
Deca-	10

In the present case, for the given compound ‘dihydrogen monoxide’ hydrogen has prefix di- which indicates the subscript 2 and oxide i.e. oxygen has prefix mono- which indicates subscript 1 to be used.
Hence combining the rule 1 and 2, the formula for dihydrogen monoxide is ${H_2}O$ .

Note :
While writing the chemical formula of molecular compound or any other compound like ionic compound, never write the subscript '1'. Writing the formula of a molecular compound is considered to be the simplest. While in case of ionic compounds (containing metal and non-metal), we have to take into account the charges of each of the elements present in the compound.