$\begin{array}{1 1} (a) NaOH+HCl \to NaclH_2O \\ (b) P_4 +5O_2 \to 2P_4O_{10}\\ (c) 2Na+cl_2 \to Nacl \\ (d) SnCl_2 +2FeCl_3 \to 2FeCl_2+SnCl_4 \end{array} $
