How many molecules of hydrogen will be required to react completely with 0.600 mol of o2 in order to form water?

The  number  of  molecules  of hydrogen  that will be required   to react  completely  with  0.600 mol  of  O2  is  calculated  as  follows
equation  for  reaction

2H2+O2  = 2H2O
by  use  of  mole  ration of H2  to O2  (2:1)  the  moles  of H2  = 0.600 x2  = 1.2  moles

by  use of Avogadro  law   that is  1  mole =  6.02  x10^23  molecules  what about  1.2  moles

=  1.2 moles  x (6.02  x10^23)/  1mole= 7.224  x10^23 molecules

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.