Cl2 (or) Br2(or) I2 reacts with hot conc. alkali solution to form
Halide + Hypohalite
Halide + Hypohalite + H2O
Halide + Halite
Halide + Halate + H2O
hot, concentrated alkali chlorine forms chloride and chlorate.
3Cl2 + 6NaOH (hot, conc) → 5NaCl + NaClO3 + 3H2O