If my wife is in menses at the time of Zauhr and at the time of Asr she is clean, must she pray Zauhr as Qada?
The Shari`ah does not want us to count these things to the seconds. If one finds at the time of Asr that they are able to take a bath and offer prayer they should do so. If a woman finds that the bleeding stopped at the time of Zauhr and could take a bath and prepare for the prayer which she neglected then she may be held responsible for neglecting the duty she owes to God.
But if it is only at the time of Asr when she comes to know that the bleeding has stopped and she does not think that the process would start again (for women generally have an idea of their routine in this regard) she should then proceed. But I do not think that the women are obliged to strictly maintain the record of every minute and decide which time fell where. They only offer prayer when they are clean and when they have taken a bath. This of course does not mean that one should keep neglecting the matter and refrain from entering into the state of ritual purity on purpose in order to avoid offering prayer which would mean a great sin in the eyes of God.