PTHH: \(KOH+HNO_3\rightarrow KNO_3+H_2O\)
\(Ba\left(OH\right)_2+2HNO_3\rightarrow Ba\left(NO_3\right)_2+2H_2O\)
Ta có: \(\left\{{}\begin{matrix}n_{KOH}=\dfrac{112}{56}=2\left(mol\right)\\n_{HNO_3}=\dfrac{189}{63}=3\left(mol\right)\end{matrix}\right.\) \(\Rightarrow\) HNO3 dư 1 mol
\(\Rightarrow n_{Ba\left(OH\right)_2}=0,5\left(mol\right)\) \(\Rightarrow m_{ddBa\left(OH\right)_2}=\dfrac{0,5\cdot171}{25\%}=342\left(g\right)\)