\(a.BaCl_2+2AgNO_3\rightarrow Ba\left(NO_3\right)_3+2AgCl\\b. n_{AgNO_3}=\dfrac{300.20\%}{170}=\dfrac{6}{17}\left(mol\right)\\ n_{AgCl}=\dfrac{24}{143,5}=\dfrac{48}{287}\left(mol\right)\\ Tacó:n_{AgNO_3\left(pư\right)}=n_{AgCl}=\dfrac{48}{287}\left(mol\right)\\ \Rightarrow H=\dfrac{\dfrac{48}{287}}{\dfrac{6}{17}}.100=47,39\%\\ c.m_{ddsaupu}=300+200-24=476\left(g\right)\\ n_{Ba\left(NO_3\right)_2}=\dfrac{1}{2}n_{AgCl}=\dfrac{24}{287}\left(mol\right)\\ n_{AgNO_3\left(dư\right)}=\dfrac{6}{17}-\dfrac{48}{287}=\dfrac{906}{4879}\left(mol\right)\\ \Rightarrow C\%_{Ba\left(NO_3\right)_2}=4,59\%;C\%_{AgNO_3\left(dư\right)}=6,63\%\)