Question

How does conservation of mass, and conservation of charge apply in chemical reactions?

Answer 1

Such laws of conservation apply ABSOLUTELY. See this old answer.

Explanation:

Chemical reactions (i) conserve mass, and (ii) conserve charge. Conservation of mass and charge are absolute. And this is why educators insist on stoichiometrically balanced equation.

There are some examples in the link, but can you represent the complete combustion reactions of butane, `C_4H_10`, and pentane, `C_5H_12`? Oxidation reduction reactions, which invoke electrons as formal particles, are another means to balance a chemical reaction.