# A chemist performs the synthesis of sodium chloride from its elements. The chemist begins with 46 grams of sodium. How many moles of chlorine are needed? 2 Na + Cl2 → 2 NaCl

## I didn't understand that is it asking about Cl (chlorine) or Cl2 (Chlorine GAS)...

We have $2$ $m o l$ of sodium metal to start; clearly we need the 1 mole of $C {l}_{2} \left(g\right)$.
$\text{Moles of sodium } = \frac{46.0 \cdot g}{22.9 \cdot g \cdot m o {l}^{-} 1} = 2 \cdot m o l$.
Given your equation, clearly we need the ONE mole of $C {l}_{2}$ gas. What is the mass of this quantity of chlorine?
It is fact that all of the elemental gases EXCEPT for the Noble Gases are diatomic: ${N}_{2} , {O}_{2} , {F}_{2} , C {l}_{2}$. Of course, all the halogens, as the elements, are diatomic, but not all are gaseous.