sodium reacts completely with 0.142kg of chlorine, forming 234g of sodium chloride. What mass of sodium reacted?

I know that for chemical changes the amounts should end up being equal, but I don't know how to set up the problem.

6 answers

It is the number of atoms, or moles, of Na which is equal to the number of atoms, or moles, of Cl in NaCl
Na = 23 grams/mol
Cl = 35.5 grams/mol

NaCl = 58.5 grams/mol

so if we ended up with 234 grams ofNaCl, that was 4 mols of NaCl

That requires 4*23 = 92 grams of Na
and
That requires 4*35.5 = 142 grams of Cl, sure enough

92.0

92 is the correct answer.

124

92.0g