When a reaction is described through a balanced equation, it is possible to determine the exact amount of each atom, ion and molecule needed on each side of the equation. Balanced equations are determined using a technique known as stoichiometry.
Each component of a balanced equation includes a stoichiometric coefficient in front of it. Stoichiometry allows chemists to determine how many moles of each reactant produce a certain number of moles of each product. An example of a balanced equation is CaCl2 + Na2CO3 = CaCO3 + 2 NaCl. The stoichiometric coefficient of two in front of the NaCl indicates two moles for every one molecule for the rest of the compounds in the equation.