Answer : A chemical formula usually represents the chemical species involved in a chemical reaction. It gives a clear information about the chemical proportions of atoms present in an chemical compound.
This chemical formula usually employs the use of chemical element symbols, numbers, etc.
Also, sometimes other symbols are also used like parentheses, dashes, brackets, commas and plus (+) or minus (−) signs.
In the given question [tex]2H_{2}O[/tex] where 2 represents the number of hydrogen atoms present in that chemical species (water molecule), The number of oxygen atom is one because it doesn't has any number before it.
The subscript [tex]H_{2}[/tex] represents the valency of hydrogen, which is 2 here. In all if we have to calculate the total number of hydrogen in this water molecule which is 4 because 2 X 2=4; this is because 2 hydrogen is multiplied with 2 valency of hydrogen.
The answer is:
Coefficient; how many water molecules there are.
