A solution of ammonia and water contains 1.20*1025 water molecules and 8.30*1024 ammonia molecules. How many total hydrogen atoms are in this solution?

Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles. We calculate as follows:

1.20*10^25 water molecules (2 atoms H / 1 molecule H2O) + (8.30*1024 ammonia molecules (3 atoms H / 1 molecules NH3) = 4.89x10^25 atoms H