the lease does not state what happens if 1 person moves out
Landlord / Tenant Lawyer
Depending on the language of the Lease, you (and each of your co-tenants) might be individually liable for the entire rent. Practically speakings, if the remaining tenants are willing to cover each month's full rental payment, then you will have nothing to worry about. However, if there is a problem and the landlord decides to file suit against the tenants, you will most likely be on the hook.
Read the lease, talk to your co-tenants, and (if necessary) call a local attorney.
If you liked my answer, please rate it "HELPFUL" or "BEST". Also, you can contact me for further detailed questions and answers at 412-904-5305. **DISCLAIMER** Michael I. Werner is licensed to practice law in the Commonwealth of Pennsylvania. This answer is based on general legal principles and is not intended for the purpose of providing specific legal advice or opinions. This answer does not constitute the establishment of an attorney-client relationship. It is always recommended that you consult with an attorney prior to taking legal actions on your own.