2. At STP, how many liters of oxygen are required to react completely with 3.6 liters

of hydrogen to form water?

2H2 (g) + O2 (g)

2H20 (g)

1.8 L.

Explanation:

The balanced equation for the mentioned reaction is:

2H₂ (g) + O₂ (g) → 2H₂O (g),

It is clear that 2.0 moles of H₂ react with 1.0 mole of O₂ to produce 2.0 moles of H₂O.

At STP, 3.6 L of H₂ reacts with (? L) of oxygen gas:

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

using cross multiplication:

1.0 mol of H₂ represents → 22.4 L.

? mol of H₂ represents → 3.6 L.

∴ 3.6 L of H₂ represents = (1.0 mol) (3.6 L) / (22.4 L) = 0.1607 mol.

To find the no. of moles of O₂ nneded to react completely with 3.6 liters (0.1607 mol) of hydrogen:

Using cross multiplication:

2.0 mol of H₂ react completely with → 1.0 mol of O₂, from stichiometry.

0.1607 mol of H₂ react completely with →? mol of O₂.

∴ The no. of moles of O₂ = (1.0 mol) (0.1607 mol) / (2.0 mol) = 0.08036 mol.

Again, using cross multiplication:

1.0 mol of O₂ represents → 22.4 L, at STP.

0.08036 mol of O₂ represents →? L.

∴ The no. of liters of O₂ will be produced = (0.08036 mol) (22.4 L) / (1.0 mol) = 1.8 L.