The following reaction is used in laboratories to produce oxygen:
2KclO3 (s) ----> 2KCl (s) + 3O2 (g)
See attachment for better equation.
To be able to solve this problem we need to realize that one thing that can be compared between reactants and products is the number of moles. By looking at the stoichiometric coefficients we see that every 2 KClO3 moles produce 3 O2 moles we can safely establish the following
2 moles KCLO3 ...
This solution consists of calculating the number moles of a molecule in an equation by considering the stoichiometric coefficients and molar masses. It also includes the calculations of volume by applying the gas law.