I have a problem that I think most of the women have. During sneezing due to force of sneeze some drops of urine came out on the pants. When I am at home then I change my pants for offer salat but when I am in university it does not possible to change there clothes and in doubt that my clothes are dirty with urine I can't offer my prayers. Is the pants become dirty due to this biological reason? Can I offer my prayers with that pants or not?
That's a hilarious problem with you and you have to take care about this. Now come to your question's answer: Your 1st priority is to change the pants and clothes which are dirty (napak) but if it is not possible and you have to pray then washed out only the area which is exactly dirty by urine and also wash your legs touched to the dirty pants than start praying. You can not perform prayer with such dirty clothes.
No you are not able to say prayer with "Napaak"" clothes and body. You are saying that you are in university so you have to first change your clothes if possible otherwise wash your clothes and body parts that where you are sure that urine dropped on that area and you see it. If your clothes color is like you can't judge that where urine dropped then you have to go home and change your wash your body and then say prayer.