Stoichiometry help #5

Question

In a soda-acid fire extinguisher, concentrated sulfuric acid reacts with sodium hydrogen carbonate to produce carbon dioxide, sodium sulfate, and water.

(a) How many moles of sodium hydrogen carbonate would be needed to react with 184.0 g of sulfuric acid?

_ mol

(b) How many moles of each product would be formed?

carbon dioxide

_ mol

sodium sulfate

_ mol

water

_ mol

Answer 1

1. Begin by writing the equation for the reaction

H₂SO₄ + NaHCO₃ ---------- Na₂SO₄ + H₂O + CO₂

1. Balance the equation (to get mole ratios):

H₂SO₄ + 2 NaHCO₃ ---------- Na₂SO₄ + 2 H₂O + 2 CO₂

The coefficients (numbers in front of the formulas) in the balanced equation give the mole ratios between the reactants and products.

What's given in the question is a mass (in g) not the moles, so the 1st thing that must be done in order to use the equation is to convert the mass to moles. This can be done only by using the molar mass of the H₂SO₄. Using the periodic table 2H + 1S + 4O = 98.08 g. This is the mass of 1 mole of sulfuric acid. (molar mass) ....... 1 mol of H₂SO₄ = 98.08 g H₂SO₄

1. Convert mass to moles using molar mass:184.0 g H₂SO₄ × 1 mol/98.08 g = 1.876 mols H₂SO₄

Balanced equation shows all mole relationships so all questions can now be answered since we now have moles of sulfuric acid.

1. 1 mol H₂SO₄: 2 mols NaHCO₃ (numbers in front come from balanced equation)

We have 1.876 mols of H₂SO₄ so twice as much NaHCO₃ is needed ⇒ 1.876 x 2 = 3.752 mols

Mols of sulfuric acid (1.876 mols) can be used to calculate mols of products based on ratios (numbers in front)

1. 1 mol H₂SO₄: 1 mol Na₂SO₄ (equal no. of mols of Na₂SO₄ will be produced)

1. 1 mol H₂SO₄: 2 mols CO₂ (twice as much CO₂ will be produced compared to H₂SO₄ used)
2. 1 mol H₂SO₄: 2 mols H₂O (twice as much H₂O will be produced compared to H₂SO₄ used)