4HCl + O₂ → 2Cl₂ + 2H₂O
mole ratio of HCl : O₂ is 4 : 1
∴ if moles of HCl = 2.3 mol
then mol of O₂ = 2.3 mol ÷ 4
= 0.575 mol
mass of O₂ = moles of O₂ × molar mass of O₂
= 0.575 mol × (16 × 2) g/mol
= 18.4 g
It is 50. The answer is 50. 10x5=50 50x1=50
Electrons, specifically valence electrons
Barium :

with +2 being the charge
Oxygen :

with -2 being the charge
The given equation can be written as:
Ba + O = BaO
Since the sum charges of Barium and Oxygen equals 0, there is no need to add subscripts.
Both Ba and O appear on the left and right side of the equation once, so there is no need to add a coefficient.
Ba + O = BaO is balanced
As common sense dictates, Mohs Scale is based on the fact that a harder material will scratch a softer one. By using a simple scratch test, you can determine the relative hardness of an unknown mineral.