Final answer:
To react completely with 8.4 moles of nitrogen dioxide, 2.8 moles of water are needed, based on the stoichiometry of the reaction.
Step-by-step explanation:
The question asks how many moles of water are needed to react completely with 8.4 moles of nitrogen dioxide (NO₂) to form nitric acid. According to the provided reaction equation:
3 NO₂ (g) + H₂O(l) → 2 HNO₃(aq) + NO(g)
It indicates that three moles of nitrogen dioxide react with one mole of water. Therefore, to find the number of moles of water needed to react with 8.4 moles of NO₂, we can set up a proportion based on the stoichiometry of the reaction:
(8.4 moles NO₂) x (1 mole H₂O / 3 moles NO₂) = 2.8 moles of water
So, 2.8 moles of water are needed to react completely with 8.4 moles of NO₂.