Hydrazine (n2h4), a rocket fuel , reacts with oxygen to form nitrogen gas and water vapor. the reaction is represented with the equation: n2h4(l) + o2(g) → n2(g) + 2h2o(g) at stp, if 4.20l of o2 reacts with n2h4, how many liters of water vapor will be produced? a) 2.10l h2o(g) b) 2.67l h2o(g) c) 5.33l h2o(g) d) 8.40l h2o(g)

D)  8.40 L H₂O(g).

Explanation:

2N₂H₄(l) + O₂(g) → N₂(g) + 2H₂O(g),

It is clear that 2.0 moles of N₂H₄ react with 1.0 mole of O₂ to produce 2.0 moles of N₂ and 2.0 moles of H₂O.

It is known that at STP: every 1.0 mol of any gas occupies 22.4 L.

using cross multiplication:

1.0 mol of O₂ represents → 22.4 L.

??? mol of O₂ represents → 4.2 L.

∴ 4.2 L of O₂ represents = (1.0 mol)(4.2 L)/(22.4 L) = 0.1875 mol.

Using cross multiplication:

1.0 mol of O₂ produce → 2.0 mol of H₂O, from stichiometry.

0.1875 mol of O₂ produce → ??? mol of H₂O.

∴ The no. of moles of H₂O = (2.0 mol)(0.1875 mol)/(1.0 mol) = 3.75 mol.

1.0 mol of H₂O represents → 22.4 L, at STP.

3.75 mol of H₂O represents → ??? L.

∴ The no. of liters of water vapor will be produced = (3.75 mol)(22.4 L)/(1.0 mol) = 8.4 L.

So, the right choice is: D)  8.40 L H₂O(g).