Please help i have no clue how to do this

How many moles of water are created if 3 moles of hydrogen react completely with excess oxygen?

Which statement is true according to the kinetic theory? a. molecules of different gases with the same mass and temperature always have the same average density. b. molecules of different gases with the same mass and temperature always have the same average volume. c. molecules of different gases with the same mass and temperature always have the same pressure. d. molecules of different gases with the same mass and temperature always have the same molecular mass. e. molecules of different gases with the same mass and temperature always have the same average kinetic energy.

20 grams of water. she poured out 15 grams. which of the following physical properties of the water changes? a .boiling point b. density c .electrical conductivity d .volume