\(a.\) \(2HNO_3+Ba\left(OH\right)_2\rightarrow Ba\left(NO_3\right)_2+2H_2O\)
\(b.\) \(n_{Ba\left(OH\right)_2}=C_M.V_{dd}=0,15.0,2=0,03mol\)
\(m_{Ba\left(NO_3\right)_2}=0,03.261=7,83g\)
\(c.\)\(n_{HNO_3}=0,03.2=0,06mol\)
\(V_{dd_{HNO_3}}=\dfrac{n}{C_M}=\dfrac{0,06}{1,2}=0,05l\)
\(d.\)\(V_{dd_{spu}}=0,05+0,15=0,2l\)
\(C_{M_{Ba\left(NO_3\right)_2}}=\dfrac{n}{V_{dd}}=\dfrac{0,03}{0,2}=0,15M\)