Question:
Answer:
The fruits (graces) of a Mass offered for the repose of a particular soul are applied when the Mass is offered. While you may find it unsettling that there’s often a long delay between when the Mass was requested and when it was offered, it helps to remember that every Mass includes a prayer for both the living and the dead. You can also offer your Holy Communion or obtain a plenary indulgence (CCC 1471-1473) for the holy souls in purgatory (or for a particular friend, relative, etc.).
The intercessions [express the fact] that the Eucharist is celebrated in communion with the whole Church, of both heaven and of earth, and that the oblation is made for her and for all her members, living and dead, who are called to participate in the redemption and salvation purchased by the Body and Blood of Christ (“20 Ways to Pray for the Souls in Purgatory,” online at cathdal.org).