<p><a href="http://www.gashalot.com/chem/dbhs.wvusd.k12.ca.us/ChemTeamIndex2.html%5B/url%5D">http://www.gashalot.com/chem/dbhs.wvusd.k12.ca.us/ChemTeamIndex2.html</a> has past National Chemistry Olympiad tests(scroll down a little). Good luck!</p>