Calculate the pH of solutions prepared by:
(d) Mixing equal volumes of 0.20 M HCl and 0.50 M HNO3.
(Assume that volumes are additive.)

Verified step by step guidance

1. Identify the nature of the acids: Both HCl and HNO3 are strong acids, meaning they completely dissociate in water.
2. Calculate the moles of HCl: Use the concentration (0.20 M) and assume a volume V to find moles of HCl as 0.20V.
3. Calculate the moles of HNO3: Use the concentration (0.50 M) and the same volume V to find moles of HNO3 as 0.50V.
4. Determine the total moles of H+ ions: Since both acids dissociate completely, add the moles of H+ from HCl and HNO3, which is 0.20V + 0.50V.
5. Calculate the concentration of H+ ions in the final solution: Since the volumes are additive, the total volume is 2V. The concentration of H+ is (0.20V + 0.50V) / 2V.
6. Determine the pH: Use the formula pH = -log[H+] to find the pH of the solution.

Key Concepts

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is neutral, while values below 7 indicate acidity and above 7 indicate alkalinity. The pH is calculated as the negative logarithm of the hydrogen ion concentration, [H+], in moles per liter. Understanding the pH scale is essential for determining the acidity of mixed solutions.

Strong Acids

Strong acids, such as HCl and HNO3, completely dissociate in water, releasing all their hydrogen ions into the solution. This complete ionization means that the concentration of hydrogen ions directly corresponds to the concentration of the acid. When mixing solutions of strong acids, the total concentration of hydrogen ions can be calculated by summing the contributions from each acid, which is crucial for determining the resulting pH.

Dilution and Volume Addition

When mixing solutions, the total volume of the resulting solution affects the concentration of solutes. Assuming volumes are additive means that the final volume is the sum of the individual volumes. This principle is important for calculating the new concentrations of the acids after mixing, as the dilution effect will influence the final pH of the solution.