Help me please, this will really mean a lot!!

Acetylene gas c2h2 undergoes combustion to produce carbon dioxide and water vapor how many grams of water are produced by the same amount of c2h2?

Which radioisotope is used to date fossils? a. oxygen-16 b. carbon-14 c. uranium-238 d. carbon-12

4al + 3o2 → 2al2o3 what does the "3" in front of o2 stand for? a) it indicates that there are 5 oxygen atoms after you add the coefficient and the subscript. b) it indicates that that there are are total of 6 oxygen atoms all bonded together as a single molecule. c) it indicates that there are 3 oxygen molecules chemically bonded to each other in the reaction. d) it indicates that there are 3 separate oxygen molecules in the reaction.