How many moles of water are in 1.23 x 10 to the 18th power water molecules

Divide the number of molecules you have by, 6.022 x 10^23. This will give you the moles of water, or the moles of anything, since there is always 6.022 x 10^23 molecules in 1 mole of substance. 

1.23x10^24 atoms/6.022x10^23 atom/mole = 2.04 mole H20 

distance, luminosity, brightness, radius, chemical composition, and temperature