Answer is: 3 mol of CO₂ must dissolve in water.
Chemical reaction: CO₂ + H₂O ⇄ H₂CO₃.
CO₂ - carbon(IV)-oxide.
H₂CO₃ - carbonic acid.
n(H₂CO₃) = 3 mol.
from reaction: n(CO₂) : n(H₂CO₃) = 1:1.
n(CO₂) : 3 mol = 1 : 1.
n(CO₂) = 3 mol.
n - amount of substance.
