given the reaction 4Na(s) +O2 -> 2Na2O How many grams of Na2O can form from 3.0g of Na? use these molecular weight Na=23g/mole and O = 16g / mole

No. of moles = mass / molecular weight
n = m / Mr
n = 3 g / 23 g/mol
n = 0.13 mol / 4
n = 0.0326 mol

Mr of Na2O = 23+23+16 = 62 g/mol

n = 0.0326 mol x 2 (because you have 2x Na2O) = 0.0652 mol

m = n x Mr
m = 0.0652 mol x 62 g/mol
m = 4.04 g

The answer should be c.