What is diatomic element?

Determine the number of moles of air present in 1.35 l at 750 torr and 17.0°c. which equation should you use? n=pv/rt what is the number of moles present? ⇒ 0.056 mol a sample of n2 gas occupying 800.0 ml at 20.0°c is chilled on ice to 0.00°c. if the pressure also drops from 1.50 atm to 1.20 atm, what is the final volume of the gas? which equation should you use? v2= p1v1t2/p2t1 what is the final volume of the gas? ⇒ 932 ml these are the answers

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.

Which of the following is true regarding chemical and nuclear reactions?