A compound containing sodium, chlorine, and oxygen is 25.42% sodium by mass. A 3.25 g sample gives 4.33 × 10^22 atoms of oxygen.What is the empirical formula?

Question

photon336 · Answer

I was thinking we could use the fact that 1 mole of any substance has 6.02*10^23 particles and we set up a ratio to find the number of moles of Oxygen 

$$\frac{ 1~mole }{ 6.02*10^{23}~atoms } =\frac{ x~moles}{ 4.33*10^{22} } => 0.072~moles~O_{2}*(\frac{ 16~grams }{ mol }) = 1.15~g~O_{2}$$

photon336 · Answer

as you can see, I multiplied the number of moles of oxygen by the molar mass of oxygen to get the number of grams. 

we know that 25.52% sodium right is in the sample so you can easily find the % of oxygen and sodium in your sample

justmeandme · Answer

How did you get 0.072 moles?

photon336 · Answer

$$\frac{ 1.15 }{ 3.25 } = 35.38$$

35.38% oxygen ~ 0.3538 oxygen
25.42% sodium ~ 0.2542 sodium
39.19% chlorine ~0.3919 chlorine 

then we look up the molar mass of each and pretend that the % are a certain number of grams. 

oxygen  1/16*(35.38g) = 2.2 mol oxygen  
chlorine 1/35*(39.19g) = 1.11 mol Cl 
sodium  1/23*(25.42g)   = 1.11 mol Na 

then we divide each one by the smallest number of moles. in this case cl 

(2.2)/(1.11) = 2 atoms of oxygen
(1.11)/(1.11) = 1 atoms of Na 
(1.11/(1.11) = 1 atom of Cl 

$$ClO_{2}Na$$

photon336 · Answer

@justmeandme I used avogadro's number to find it out 1 mole of any substance has /6.02*10^23 particles. then I set up a ratio to find the number of moles of oxygen in our sample.

justmeandme · Answer

@Photon336 would it be wrong if I chose Na to be the smallest number of moles?

photon336 · Answer

nope can chose either one