What is Usually expressed by a chemical formula?

Answer 1

A chemical or molecular formula is a way of representing a particular compound. It is written using the symbols of the constituent elements and indicating the number of atoms of each elements in 1 molecule by subscripts. for example, Na2CO3 represents Sodium carbonate. It tells us that Sodium Carbonate is composed of Sodium(Na) Carbon(C) and Oxygen(O). It also tells us number of each type of atom in 1 molecule, Sodium Carbonate has 2 sodium, 1 carbon and 3 oxygen atoms in one molecule.

It also tells us the mass of 1 mole(6.0225*1023 molecules) of the substance. Mass of 1 mole = summation of (Atomic Mass of each type of element * no. of atoms of that element in the molecule). Here mass of 1 mole of Na2CO3= 23*2 + 12*1 + 16*3 grams

=106 grams.

chemical formula also lets us find relative % of each element in a given sample of compound. We can also find total mass of respective elements.

Chemical formula are used in chemical equations to describe chemical reactions.

Note that these formulas don't indicate structure of molecules.

Answer 2

A chemical formula typically expresses the composition or structure of a chemical compound. It shows the elements present in the compound and their respective ratios or quantities. For example, the chemical formula H2O represents water, where H indicates hydrogen atoms and O indicates oxygen atoms, with two hydrogen atoms bonding with one oxygen atom.