\(a.m_{Ba}=1.5\cdot137=205.5\left(g\right)\)
\(b.m_{N_2}=0.2\cdot28=5.6\left(g\right)\)
\(c.m_{HNO_3}=1.5\cdot63=31.5\left(g\right)\)
\(d.m_{CuSO_4}=0.5\cdot160=80\left(g\right)\)
\(e.m_{HCl}=2.5\cdot36.5=91.25\left(g\right)\)
\(f.m_{O_2}=3\cdot32=96\left(g\right)\)