A 0.205 M NaOH solution is used to titrate 20.0 mL of a solution of H₂SO₄. If 45.6 mL of the NaOH solution is required to reach the endpoint, what is the molarity of the H₂SO₄ solution?
H₂SO₄(aq) + 2NaOH(aq) → 2H₂O(l) + Na₂SO₄

Verified step by step guidance

1. Step 1: Write the balanced chemical equation for the reaction. The reaction is already provided: H₂SO₄(aq) + 2NaOH(aq) → 2H₂O(l) + Na₂SO₄. This shows that 1 mole of H₂SO₄ reacts with 2 moles of NaOH.
2. Step 2: Calculate the moles of NaOH used in the titration. Use the formula: moles = molarity × volume. Convert the volume of NaOH solution (45.6 mL) to liters by dividing by 1000, then multiply by the molarity of NaOH (0.205 M).
3. Step 3: Use the stoichiometry of the reaction to determine the moles of H₂SO₄. From the balanced equation, 1 mole of H₂SO₄ reacts with 2 moles of NaOH. Divide the moles of NaOH by 2 to find the moles of H₂SO₄.
4. Step 4: Calculate the molarity of the H₂SO₄ solution. Use the formula: molarity = moles / volume. The moles of H₂SO₄ were determined in Step 3, and the volume of the H₂SO₄ solution is given as 20.0 mL. Convert this volume to liters by dividing by 1000, then divide the moles of H₂SO₄ by this volume.
5. Step 5: Ensure the units are consistent and double-check the calculations. The final molarity of the H₂SO₄ solution will be in moles per liter (M).

Key Concepts

Titration

Titration is a quantitative analytical technique used to determine the concentration of a solute in a solution. It involves the gradual addition of a titrant (a solution of known concentration) to a sample solution until a reaction endpoint is reached, often indicated by a color change. In this case, NaOH is the titrant used to neutralize H₂SO₄.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows us to determine the relationships between the amounts of substances involved. For the reaction between H₂SO₄ and NaOH, the stoichiometric ratio is 1:2, meaning one mole of H₂SO₄ reacts with two moles of NaOH.

Molarity

Molarity is a measure of concentration defined as the number of moles of solute per liter of solution. It is expressed in moles per liter (M). To find the molarity of the H₂SO₄ solution in this titration, we will use the volume of NaOH used, its molarity, and the stoichiometric relationship from the balanced equation to calculate the moles of H₂SO₄ present.