Needed asap very much appreciated ! chemistry

What will most likely happen when two bromine atoms bond together?

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms

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