3) One mole = 6.0221415 x 10^23 molecules
23 x [ 6.0221415 x 10^23] =1.385092545 x 10^24 - molecules in 23 moles of Sodium.
8)
Convert from grams into liters:
46 g of Cl_2 (chlorine)
Convert from grams to cubic centimeters using the density 0.003214 g/cm^3 (at STP) of Cl_2:
46 g (1/(0.003214 g/cm^3)) = 14310 cm^3
Convert to milliliters using the relation 1 cm^3 = 1 mL:
14310 cm^3 ((1 mL)/(1 cm^3)) = 14310 mL
Convert to liters using the relation 1000 mL = 1 L:
14310 mL ((1 L)/(1000 mL)) = 14.31 L
7) Sorry, I don't know this one!.