Is N2 a compound or an element

If 22.5 liters of oxygen reacted with excess of hydrogen, how many liters of water vapor could be produced?

Which of the following is described by the equation h2o(s)+ heat=h2o(i) a freezing melting condensing evaporating

How does a sample of helium at 15 degree celsius compare to a sample of helium at 215 k? a) the helium at 15 degrees celsius has a higher average kinetic energy that the sample at 215 k. b) the helium at 15 degrees celsius has lower nuclear energy that the sample at 215 k. c) the helium at 15 degrees celsius has slower- moving atoms that the sample at 215 k. d) the helium at 15 degrees celsius has smaller atoms than the sample at 215 k.