Which equation shows a conservation of mass?
(1) Na + Cl2 --> NaCl
(2) Al + Br2 --> AlBr3
(3) H2O --> H + O2
(4) PCl5 --> PCl3 + Cl2
(1) Na + Cl2 --> NaCl
(2) Al + Br2 --> AlBr3
(3) H2O --> H + O2
(4) PCl5 --> PCl3 + Cl2