A compound containing sodium, chlorine, and oxygen is 25.42% sodium by mass. A 3.25 g sample gives 4.33*1022 atoms of oxygen. What is the empirical formula?

step one

calculate the % of oxygen

from avogadro constant

1moles = 6.02 x 10 ^23 atoms

what about 4.33 x10^22 atoms

= (4.33 x 10^ 22 x 1 mole) / 6.02 10^23 = 0.0719 moles

mass = 0.0719 x16 = 1.1504 g

% composition is therefore = (1.1504/3.25) x100 = 35.40%

step two

calculate the % composition of chrorine

100 - (25.42 + 35.40) = 39.18%

step 3

calculate the moles of each element

that is

Na = 25.42 / 23=1.1052 moles

Cl = 39.18 / 35.5=1.1037moles

O = 35.40/16 = 2.2125 moles

step 4

find the mole ratio by dividing each mole by 1.1037 moles

that is

Na = 1.1052/1.1037=1.001

Cl = 1.1037/1.1037 = 1

0=2.2125 = 2

therefore the empirical formula = NaClO2