Chlorine, itself is a gas and can be used for chemical disinfection, generally on a commercial basis. What most of us have available is a solution of sodium hyperchlorite (NaClO) or household bleach, which works through oxidation. As with many solutions, the individual ions will be in a state of flux. In the scenario you have presented, if the container was overfilled, ensuring that no air was present in the container when it was sealed (must be air tight), there would likely be no significant loss of chlorine. However, as soon as you opened the container, a degree of off gassing would occur. If the container was not filled all of the way or if not air tight, additional off gassing would occur.

Pete