§1. For a member of the Christian faithful validly to receive sacramental absolution given to many at one time, it is required not only that the person is properly disposed but also at the same time intends to confess within a suitable period of time each grave sin which at the present time cannot be so confessed.
§2. Insofar as it can be done even on the occasion of the reception of general absolution, the Christian faithful are to be instructed about the requirements of the norm of §1. An exhortation that each person take care to make an act of contrition is to precede general absolution even in the case of danger of death, if there is time.
Source: Code of Canon Law (Vatican.va)