Type the correct answer in the box. express the answer to two significant figures. given: n2 + 3h2 → 2nh3 use the bond energies to calculate the change in enthalpy for the reaction. the enthalpy change for the reaction is [ ]kilojoules.

Which is true of chemicals? a. things containing chemicals always cost a lot of money. b. chemicals are never dangerous. c. chemicals are in many substances in a home. d. chemicals are rarely found on earth.

Hot air balloons float in the air because of the difference in density between cold and hot air. in this problem, you will estimate the minimum temperature the gas inside the balloon needs to be, for it to take off. to do this, use the following variables and make these assumptions: the combined weight of the pilot basket together with that of the balloon fabric and other equipment is w. the volume of the hot air inside the balloon when it is inflated is v. the absolute temperature of the hot air at the bottom of the balloon is th (where th> tc). the absolute temperature of the cold air outside the balloon is tc and its density is ďc. the balloon is open at the bottom, so that the pressure inside and outside the balloon is the same. as always, treat air as an ideal gas. use g for the magnitude of the acceleration due to gravity.

Which piece of equipment would me most useful for measuring the volume of some water? a. pan balance b. graduated cylinder c. tweezers d. flask quick