From the College Board:( www.collegeboard.com )
"Chemistry: The Chemistry test assesses your understanding of general chemistry at the college preparatory level. The test is an hour long and consists of 85 questions. The use of a calculator is not permitted. Numerical calculations are limited to simple arithmetic. A periodic table indicating the atomic numbers and masses of elements is provided for all test administrations."
"Subject Tests, one-hour, mostly multiple-choice tests, measure how much students know about a particular academic subject and how well they can apply that knowledge."
"Many colleges require or recommend one or more of the Subject Tests for admission or placement. Used in combination with other background information (your high school record, scores from other tests like the SAT I, teacher recommendations, etc.), they provide a dependable measure of your academic achievement and are a good predictor of future performance."
I recommend consulting the college board website with respect to the SAT II in chemistry, at the SAT II learning center. There is also a special (PDF) publication on the various SAT II examinations, including the SAT II in chemistry, here.
The College Board Website