Question

Question #30788

Answer 1

From the balanced equation 46 grams of `Na`reacts with 71 grams of `Cl_2` gas to form 117 grams of `NaCl` (numbers obtained from the molar mass/atomic mass)

The law of conservation of mass says that the mass of reactants equals the mass of products.

We can say that 2 moled of `Na` reacts with 1 mole of `Cl_2` molecule to form 2 moles of `NaCl`.

We see the 117 g of `NaCl` is 117 g/117 g/mol = 1 mol

(Mole = mass/molar mass)

Hence 1 mole of `NaCl` will require 1 mole of `Cl2` molecule (from the stoichiometry).

1 mole of `Cl_2` molecule is equivalent to 2 moles of `Cl` atom and hence 2* 35.5 g = 71 g.

I would be curious to find out how you got 69.9 grams.

The questioner asked how one can set up the Stoichiometry of this equation. Stoichiometry is nothing but the ratio of reacting species in the balanced chemical equation. In the above equation, one can write,

mol `Cl_2`: mol `NaCl` is 1 : 1

Hence the masses of `Cl_2` and `NaCl` would be equivalent.