The reaction between solid sodium and iron(III) oxide is one in a series of reactions that inflates an automobile airbag.

6 Na(s) + Fe2O3(s) 3 Na2O(s) + 2 Fe(s)

If 171.0 g Na and 213.5 g Fe2O3 are used in this reaction, what is the mass of excess reactant that remains after the reaction is complete?

To find the mass of the excess reactant that remains after the reaction is complete, we first need to determine the limiting reactant.

Step 1: Calculate the molar mass of each substance.
Molar mass of Na: 22.99 g/mol
Molar mass of Fe2O3: (55.85 g/mol × 2) + (16.00 g/mol × 3) = 159.69 g/mol

Step 2: Determine the number of moles for each substance.
Number of moles of Na = mass of Na / molar mass of Na
= 171.0 g / 22.99 g/mol
= 7.44 mol

Number of moles of Fe2O3 = mass of Fe2O3 / molar mass of Fe2O3
= 213.5 g / 159.69 g/mol
= 1.34 mol

Step 3: Calculate the mole ratio of the reactants using the balanced equation.
From the balanced equation: 6 Na : 1 Fe2O3
So, the mole ratio is 6 : 1.

Step 4: Determine the limiting reactant.
The limiting reactant is the one that is completely consumed in the reaction, limiting the amount of product that can be formed. It can be determined by comparing the mole ratios of the reactants.

Since the mole ratio of Na to Fe2O3 is 6:1, and there are 7.44 moles of Na and 1.34 moles of Fe2O3, we can see that Fe2O3 is the limiting reactant since you need 6 moles of Na for every 1 mole of Fe2O3.

Step 5: Calculate the amount of excess reactant used.
To calculate the amount of excess reactant used, we need to determine the theoretical amount of the excess reactant that would be consumed if the limiting reactant is completely consumed.

From the balanced equation: 6 Na : 1 Fe2O3
Since we have 1.34 moles of Fe2O3, we would need 6 moles of Na for 1.34 moles of Fe2O3.

Amount of Na needed for 1.34 moles of Fe2O3 = (6 moles/1.34 moles) × 1.34 moles of Na
= 6 moles of Na

We used exactly the required amount of Na, so there is no excess reactant remaining.

Therefore, the mass of the excess reactant that remains after the reaction is complete is 0 grams.