If 4.0 mol of NO and 4.0 mol of O2 are combined, how many moles of NO2 can be produced?
2NO + O2 —> 2NO2

There will be 4 moles of NO2 produces at the end of the reaction.

Explanation:

First of all, you should consider that the limiting reactant is NO, since it's the first it's going to end in the reaction.

After that, the conversion factor must be done with the limiting reactant (NO). So since you have 4 mol of NO and the relation of NO with NO2 its 2:2, you will end up having 4 moles of NO2.

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation: