First, I should mention the book. "Química" by Raymond Chang is a well-known textbook in the field of chemistry. The 13th edition might have some updates or changes from previous editions, so that's worth noting. However, the user wants the post to be verified as far as the PDF version. It's important to emphasize that using unauthorized PDFs might be illegal and against copyright laws. But since the user is asking for a verified post, I have to walk a fine line between providing information and not promoting piracy.