11.5 grams of sodium metal are placed in a container with excess chlorine gas. Once the reaction is complete, 29.0 grams of sodium chloride are measured. What mass, in grams, of chlorine gas reacted?

17.6 g of chlorine gas reacted.

Explanation:

1) Chemical equation:

2Na + Cl₂ (g) → 2NaCl (s)

2) Mole ratios:

2 mol Na : 1 mol Cl₂ : 2 mol NaCl

3) Number of moles of sodium chloride (NaCl) measured (produced):

Number of moles = mass in grams / molar mass

Molar mass of NaCl = 58.44 g/mol

Number of moles of NaCl = 29.0 g / 58.44 g/mol = 0.496 mol

4) Number of moles of chlorine gas (Cl₂) reacted:

From the stoichiometric mole ratios:

1 mol Cl₂ / 2 mol NaCl = x / 0.496 mol NaCl

x = 0.496 mol NaCl / 1 mol Cl₂ / 2 mol NaCl = 0.248 mol Cl₂.

5) Convert 0.248 mol Cl₂ into mass in grams:

mass in grams = molar mass * number of moles molar mass of Cl₂ = 70.9 g/mol mass in grams = 70.9 g/mol * 0.248 mol = 17.6 g ← answer