Question

What mass of oxygen is contained in a 5.8 g sample of NaHCO3?

Answer 1

Molar mass of NaHCO3 is 83.9. moles of Na...O3= 5.8/83.9
=0.0691
for every mole of Na..O3 there are 3 O
n(O) = n(NaHCO3) x3
        = 0.207
mass of O is the moles x molar mass (16)
therefore the mass of O is 3.3 grams