If my wife is in menses at the time of Zuhr and at the time of Asr she is clean, must she pray Zuhr as Qadah?
The Shari`ah does not want us to count such things to the second. If a lady finds at the time of Asr that she is able to take a bath and offer the prayer, she should do so. If she finds that the bleeding had stopped at the time of zuhr and she could have taken the bath and prepared for the prayer which she neglected then she would be held responsible for neglecting the obligation she owes to God.
But if it is only the time of Asr when she came to know that the bleeding had 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 women are obliged to strictly maintain the record of every minute and decide which time fell where. They are only liable to offer the prayer when they are clean and when they have taken the bath. This of course does not mean that a lady 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.