In the explosion of a hydrogen-filled balloon, 0.20 g of hydrogen reacted with 1.6 g of oxygen. How many grams of water vapor are formed? (Water vapor is the only product.) What equation should I use?

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".