when 2.40 moles of sodium react with 5.90 moles of chlorine gas in the reaction shown above, how many moles of sodium chloride are produced?

First we look at the chemical reaction:

2 Na + Cl₂ → 2 NaCl

Now we should see which is the limiting reagent, so we construct the following reasoning:

if 2 moles of Na reacts with 1 mole of Cl₂

then 2.4 moles of Na reacts with X moles of Cl₂

X = (2.4 * 1) / 2 = 1.2 mole of Cl₂ (way lower that the available quantity of chlorine).

So the limiting reagent is sodium, and from here we can calculate the number of moles of NaCl produced.

if 2 moles of Na produces 2 moles of NaCl

then 2.4 moles of Na produces Y moles of NaCl

Y = (2.4 * 2) / 2 = 2.4 moles fo NaCl (sodium chloride)