In an exploration lab, we tested reactants which included; a white, and liquid. Depending on which solid/liquid we used, they typically produced ~50% of their mass to CO2 gas. Switching between the reactants, a mass relationship does not apply because they reacted differently and had different produce. A molar relationship does exist because they are balanced equations and the products and reactants may be different, but that are still composed of the same elements. Meaning that is a number of moles of a reactant is mixed, it will produce so many moles of whatever it may be.