Question

What is stoichiometry and what is it used for?

Answer 1

What is `"stoichiometry"`? Well, it is the principle that `"garbage in equals out...."`

Explanation:

And what underlies it? Well, the principle that MASS is conserved in a chemical reaction....and our chemical equations that represent these reactions must reflect this mass equivalence...

See this old answer.... And see here. And elsewhere...