Determine the volume of carbon dioxide that must be passed through 300 g

Determine the volume of carbon dioxide that must be passed through 300 g of a solution containing 15 g of barium hydroxide so that its concentration drops to 4%.

The reaction of passing carbon dioxide through a solution of barium hydroxide:

Ba (OH) ₂ + CO₂ = BaCO₃ ↓ + H₂O.

Let’s compose an expression:
If x mol of СО₂ is 44x g,
then 171x g of Ba (OH) ₂ enters into the reaction.
Then (15 – 171x) g Ba (OH) ₂ remained in the solution,
and 197x g of BaCO₃ was precipitated.
Accordingly, the mass of the initial solution (300 + 44x -197x) g.

We get the equation:
n (CO₂) = (15 – 171x) / (300 + 44x – 197x) = 0.04.
Find x:
x = 0.018 mol.
V (CO₂) = n • Vm = 0.018 • 22.4 = 0.4 liters.