\(HCO_3^-+OH^-\rightarrow CO_3^{2-}+H_2O\)
\(Ba^{2+}+CO_3^{2-}\rightarrow BaCO_3\downarrow\)
\(n_{Ba^{2+}}=0,15+0,1=0,25\left(mol\right)\)
\(n_{HCO_3^-}=0,2\left(mol\right)\)
\(n_{OH^-}=0,2\left(mol\right)\)
\(\Rightarrow n_{CO_3^{2-}}=0,2\left(mol\right)\)
\(\Rightarrow n_{BaCO_3\downarrow}=0,2\left(mol\right)\)
\(\Rightarrow m_{BaCO_3\downarrow}=0,2.197=39,4\left(g\right)\)