Question

How many liters of oxygen are required to react completely with 2.4 liters of hydrogen to form water? `2H_2(g) + O_2(g) -> 2H_2O(g)`?

Answer 1

Why `1.2*L` precisely..........

Explanation:

Recall old Avogadro's hypothesis...........

`"Equal volumes of gases contain AN EQUAL NUMBER of PARTICLES"`

And thus if there are `2.4*L` of dihydrogen, stoichiometric equivalence requires `1.2*L` of dioxygen. How many litres of water gas result?

Answer 2

`1.2 L`

Explanation:

Know that one mole of any gas at STP takes up 22.4 liters. So 2.4 L of hydrogen is `0.107142857 mols H_2`.

Since `H_2` reacts with `O_2` in a 2:1 ratio, to completely react the two you will need half as much oxygen as hydrogen.

`"mols " O_2= (0.107142857 mols H_2)/2`

`"mols " O_2 = 0.053571429 mols`

To find liters of oxygen, just multiply the moles above by 22.4 liters.

`"liters "O_2 = 0.053571429 mols * 22.4 L/(mols)`

`"liters " O_2 = 1.2L`