\(a.Fe+CuSO_4\rightarrow FeSO_4+Cu\\ b.Đặt:n_{Fe\left(pứ\right)}=x\left(mol\right)\\ m_{tăng}=m_{Cu\left(sinhra\right)}-m_{Fe\left(pứ\right)}=64x-56x=51-50\\ \Rightarrow x=0,125\left(mol\right)\\ m_{Cu}=0,125.64=8\left(g\right)\\ c.n_{FeSO_4}=n_{Fe\left(pứ\right)}=0,125\left(mol\right)\\ \Rightarrow m_{FeSO_4}=0,125.152=19\left(g\right)\)