Two 25.0-mL samples, one 0.100 M HCl and the other 0.100 M HF, are titrated with 0.200 M KOH. c. Which titration curve has the lower initial pH?

Verified step by step guidance

1. Step 1: Understand the nature of the acids involved. HCl is a strong acid, while HF is a weak acid.
2. Step 2: Recall that the initial pH of a solution is determined by the concentration and strength of the acid.
3. Step 3: For strong acids like HCl, they dissociate completely in water, leading to a higher concentration of H+ ions compared to weak acids like HF, which only partially dissociate.
4. Step 4: Calculate the initial pH for each solution. For HCl, use the formula pH = -\log[H^+], where [H^+] is the concentration of HCl. For HF, consider the acid dissociation constant (Ka) to find [H^+].
5. Step 5: Compare the initial pH values calculated for HCl and HF. The solution with the higher concentration of H+ ions (lower pH) will be the one with the strong acid, HCl.

Key Concepts

Strong vs. Weak Acids

Strong acids, like HCl, completely dissociate in solution, resulting in a higher concentration of hydrogen ions (H+) and a lower initial pH. In contrast, weak acids, such as HF, only partially dissociate, leading to a higher initial pH due to a lower concentration of H+ ions in solution.

Titration Curves

A titration curve plots pH against the volume of titrant added. The shape of the curve is influenced by the strength of the acid and base involved. For strong acid-strong base titrations, the initial pH is low, while weak acid-strong base titrations show a more gradual increase in pH, reflecting the acid's partial dissociation.

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 logarithmically related to the concentration of H+ ions; thus, a small change in pH corresponds to a significant change in H+ concentration, which is crucial for understanding the initial conditions of the titration.