\(a.n_{Ba_3\left(PO_4\right)_2}=\dfrac{120,2}{601}=0,2\left(mol\right)\\ b.Sốphântử:3+\left(1+4\right).2=13\left(phântử\right)\\ c.n_{Ba}=3n_{Ba_3\left(PO_4\right)_2}=0,6\left(mol\right)\\ \Rightarrow m_{Ba}=82,2\left(g\right)\\ n_P=2n_{Ba_3\left(PO_4\right)_2}=0,4\left(mol\right)\\ \Rightarrow m_P=0,4.31=12,4\left(g\right)\\ n_O=8n_{Ba_3\left(PO_4\right)_2}=1,6\left(mol\right)\\ \Rightarrow m_O=1,6.16=25,6\left(g\right)\)