How does stoichiometry relate to the law of conservation?
Stoichiometry simply means "in the right measure". If I start with 10 g of reactant I must finish with 10 g of product. Mass is conserved!
To reiterate, mass is conserved in EVERY chemical reaction. A 10 g quantity of reactant, can give at most a 10 g quantity of product. Since atoms and molecules have definite masses, this is why teachers go to such lengths to ensure that equations are balanced, or rather ensure that equations are stoichiometric.
Is mass conserved in a nuclear reaction? Why or why not?