Question

Consider separate aqueous solutions of \(\mathrm{HCl}\) and \(\mathrm{H}_{2} \mathrm{SO}_{4}\) with the same molar concentrations. You wish to neutralize an aqueous solution of NaOH. For which acid solution would you need to add more volume (in milliliters) to neutralize the base? a. the HCl solution b. the \(\mathrm{H}_{2} \mathrm{SO}_{4}\) solution c. You need to know the acid concentrations to answer this question. d. You need to know the volume and concentration of the NaOH solution to answer this question. e. c and d Explain.

Short answer

a. the HCl solution

Step-by-step solution

Write the balanced neutralization reactions for both acids

First, we need to write down the balanced chemical equations for the neutralization reactions of HCl and H₂SO₄ with NaOH. 1. HCl + NaOH -> NaCl + H₂O 2. H₂SO₄ + 2 NaOH -> Na₂SO₄ + 2 H₂O In equation 1, one mole of HCl reacts with one mole of NaOH. In equation 2, one mole of H₂SO₄ reacts with two moles of NaOH.

Determine the stoichiometry of the reactions

Comparing these reactions, we can infer that one mole of H₂SO₄ can neutralize twice the amount of NaOH as one mole of HCl. It's important to note that 1 mole of H₂SO₄ has twice the neutralizing power, given that it disassociates into two H⁺ ions.

Compare the volumes of acids required for neutralization

Since both the HCl and H₂SO₄ solutions have the same molar concentrations, the volume required to neutralize a given amount of NaOH would be inversely proportional to their neutralizing power. In this case, given that one mole of H₂SO₄ can neutralize twice the amount of NaOH as one mole of HCl, we can conclude that we would need a smaller volume of the H₂SO₄ solution to neutralize the same amount of NaOH.

Choose the correct answer from the available options

Based on our analysis, we can conclude that we would need to add more volume of the HCl solution to neutralize the NaOH solution compared to the H₂SO₄ solution. Hence, the correct answer is: a. the HCl solution

Key concepts

Stoichiometry

Stoichiometry is a fundamental concept in chemistry that helps us understand the quantitative relationships in chemical reactions. It allows us to calculate how much reactant is required or how much product will be formed in a given chemical equation. When dealing with neutralization reactions, stoichiometry helps us determine the precise amount of acid needed to completely react with a base.

In the balanced chemical equations provided:

• For the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), it takes one mole of HCl to neutralize one mole of NaOH.
• For sulfuric acid (H₂SO₄), two moles of NaOH are required to be neutralized by one mole of H₂SO₄, indicating it has twice the neutralizing capability compared to HCl.

This stoichiometric difference is essential because it informs us about the volumes of acid solutions required for complete neutralization. Understanding stoichiometry helps in accurately predicting and comparing the amounts of reagents involved in reactions.

Acid-Base Chemistry

Acid-base chemistry is a branch of chemistry that studies the properties of acids and bases, their reactions, and their neutralization. Neutralization is a process where an acid reacts with a base to form water and a salt, which is key to many chemical processes.

In the exercise, both HCl and H₂SO₄ are regarded as acids because they release hydrogen ions (H⁺) when dissolved in water. The difference lies in their disassociation:

• HCl disassociates to form a single H⁺ ion per molecule.
• H₂SO₄ disassociates to release two H⁺ ions per molecule, doubling its acidic power.

Thus, one molecule of H₂SO₄ can neutralize an equivalent of two molecules of NaOH, whereas one molecule of HCl can only neutralize one molecule of NaOH. Acid-base chemistry helps us understand these interactions and calculate the needed conditions for neutralization.

Molarity

Molarity is a concentration measurement expressed as the number of moles of a solute per liter of solution. It is crucial for determining how much of a reagent is present in a chemical reaction.

In the case of neutralization, knowing the molarity of our solutions is key to determining how much volume of acid is needed to neutralize a given base. For example:

• If both HCl and H₂SO₄ solutions have the same molarity, it means there are equal amounts of reactive acid particles in an equivalent volume.
• Despite having the same molarity, H₂SO₄ solutions possess twice the neutralizing capacity per mole, as each mole can release two H⁺ ions.

Thus, a smaller volume of H₂SO₄ will suffice to neutralize a given base, compared to HCl. Understanding molarity helps to fine-tune how much solution is necessary in practical chemical reactions and experiments.