Textbooks - question about Chemistry

<p>So the new Chemistry textbook costs around 100 dollars. It is the newest, 6TH edition of "Chemical Principles" by Zumdahl. Have any of you guys compared the 5th and the 6th edition? I just wanted to know if the work problems are the same or not. If they are the same, I can just buy the 5th edition (for 5 dollars). </p>

<p>Let me know your two cents! Any input is appreciated. </p>

<p>PS: Any good sites to buy textbooks (besides amazon.com, half.ebay.com) ?</p>

<p>Alibris is good for older textbooks.</p>