The following pictures represent solutions at various stages in the titration of sulfuric acid H2A (A2- = SO4 2-) with aqueous NaOH. (Na+ ions and water molecules have been omitted for clarity.)

. (b) Which solution has the highest pH? Draw a picture that represents the solution prior to addition of any NaOH.

Verified step by step guidance

1. Identify the stages of titration in the provided images. The images show different stages of the titration process of sulfuric acid (H2SO4) with NaOH.
2. Determine which solution has the highest pH. The solution with the highest pH will be the one where the titration is complete, and there is an excess of NaOH.
3. Analyze the images to find the solution with the highest concentration of OH- ions. This will indicate the highest pH.
4. Draw a picture representing the solution prior to the addition of any NaOH. This will show only H2SO4 molecules and water molecules.
5. Ensure the picture includes H2SO4 dissociating into H+ and SO4 2- ions in water, without any Na+ or OH- ions present.

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 (in this case, NaOH) to a solution containing the analyte (sulfuric acid, H2A) until the reaction reaches its endpoint, which is often indicated by a color change or a pH change. Understanding the titration process is crucial for determining the pH at various stages of the reaction.

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral. The pH is determined by the concentration of hydrogen ions (H+) in the solution; lower pH values indicate higher concentrations of H+, while higher pH values indicate lower concentrations. In the context of the titration, the pH will change as NaOH is added, affecting the acidity of the sulfuric acid solution.

Acid-Base Neutralization

Acid-base neutralization is a chemical reaction between an acid and a base that produces water and a salt. In this titration, sulfuric acid (H2A) reacts with sodium hydroxide (NaOH) to form water and sodium sulfate (Na2SO4). This reaction is essential for understanding how the pH changes during the titration process, as the neutralization will lead to a decrease in acidity and an increase in pH as more NaOH is added.