chem
posted by manny .
Ok... i have no idea how to do this problem.... if anybody can help, that would be very much appreciated
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67.) Oil spreads on water to form a film about 100 nm thick. How many square kilometers of ocean will be covered by the slick formed when one barrel of oil is spilled (1 barrel = 31.5 U.S. gallons)
***Answer has two sigifgs
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Thanks!!!!!!

The volume of the spill (area*thickness) has to equal the volume spilled.
Watch units. 
ok thanks!!
I got 1.2 km^2 for the answer.