Dear Student,
When chlorine gas is passed through cold solid sodium hydroxide solution it results in the formation of sodium chloride , sodium chlorate and water. And sodium chlorate is also known as sodium hypochlorite.
Balanced reaction is given below :
Cl2 (g) + 2NaOH(s) -----> NaCl(s) + NaClO(s) + H2O(l)
​Regards