There are several laws that govern the composition of matter and chemical reaction. These are, the law of conservation of mass, the law of definite proportions, the law of multiple proportions and the law of reciprocal proportions.
Atomic mass is the average mass of naturally occurring isotopes, which is compared to the mass of one atom of carbon-12 a.m.u.
The molecular mass of a molecule is the sum of the atomic masses of all the atoms present in that molecule.
Formula mass of the substance is sum of the atomic masses of all the atoms present in the formula unit of the substance.
Molar mass is the mass in grams of one mole of a substance.
Mole is the amount of substance that contains as many elementary particles (atoms, ions, molecules or formula units) as there are atoms in 12g of carbon-12 isotope.
Avogadro's number, the number of particles i.e. atoms, ions, molecules or formula units in one mole of substance equal to 6.02x1023 .
The empirical formula is the formula which describes the smallest or the least ratio of the combining atoms of different elements present in a molecule.
The Molecular formula shows the actual number of the combining atoms of all the elements present in a molecule and is always an integer multiple of empirical formula.
Chemical reaction is a change in which the composition of substance is changed and new substances are formed. Chemical reactions can be divided into five different types. Decomposition reaction combination reaction, single replacement reaction, doubles replacement reactions and the combustion reactions.
A chemical equation represents the chemical change or reaction, showing reactants on the left side of an arrow and products on the right. The equation is balanced by placing co-efficient in front of the formulas, so the numbers of atoms of each element are same on each side of an arrow.
Amounts of reactants and products formed can be calculated from the balanced equation for a reaction by using the mole-ratios relating. &reactants and products.