A chemist pumps hydrogen gas (h2) from a tank into a reaction vessel containing 0.734 mol o2. the gases react to form water. if all of the available o2 reacts, how many moles of h2 are used?

Hydrogen + oxygen - > water

2H2 + O2 - > 2H2O (balanced)

2 moles of hydrogen gas will react with 1 mole of oxygen to produce 2 moles of water.

following that ratio, 0.734 mole of oxygen must need 0.734 * 2 moles of hydrogen to fully react.

answer is 1.468 moles of hydrogen.