Examples

Validation of Water Samples

Problem. How to validate a water sample (charge balance and other parameters)?
Problem. What is the equilibrium composition and alkalinity of a water sample with incomplete analytical data?
Problem. What is the optimal parameter (cation or anion) for charge balance adjustment?

The Carbonate System

Problem. What is the pH of a 1 millimolar CO₂ solution?
Problem. What are the equivalence points of the following three solutions: (i) 0.001 molar H₂CO₃, (ii) 0.001 molar NaHCO₃, and (iii) 0.001 molar Na₂CO₃?
Problem. Carbonate Species vs. pH – Closed System
Problem. Carbonate Species vs. pH – Open System
Problem. Calcite Carbonate System

pH Calculations

Problem. What is the pH of a given phosphate buffer before/after addition of NaOH and HCl?
Problem. Given is a 0.001 molar NH₄Cl solution. What is the pH after addition of 0.2 mmol NH₃?
Problem. What is the pH of an acid rain sample?
Problem. What is the pH of an extremely dilute acid (10^-8 M HCl)?
Problem. Given is a NaOH solution. How does the pH change when the solution is in contact with air for a long time? How much CO₂ from air is captured in the solution?

Acids and Bases

Problem. What is the pH and the concentration of hydrogen sulfate of a 1.2 mM sulfuric acid?
Problem. Addition of 0.2 mM HCl to a given water sample.
Problem. Strong acids (HCl, HNO₃, H₂SO₄) without and with ionic activity corrections.
Problem. Phosphoric acid as a polyprotic acid.
Problem. Phosphoric acid and sodium phosphates.
Problem. Calculate the pH value for all acids given here for three different concentrations (1, 10, and 100 mM).

Dilution and Mixing

Problem. 40 mL of 2.5 molar H₂SO₄ solution will be diluted to 2 L. What is the pH of the final solution?
Problem. 100 mL of 0.01 molar HCl and 50 mL of 0.05 molar NaCl are mixed. What is the pH of the final solution?

Titration

Dosage / Addition of Chemicals

Problem. Given is a groundwater with pH 6.9. How much HNO₃ and how much H₂SO₄ are needed to obtain pH 3?
Problem. Given is a water sample with pH 7.9. What is the pH after addition of 0.3 mM KOH? What is the impact of calcite precipitation?

Mineral Phases

Environmental Chemistry

Problem. Given is pH and total ammonia. What is the NH₃ concentration (which is toxic to fish)?
Problem. What is the chemical composition of pristine rainwater?
Problem. What is the pH of a given acid rain sample?

[last modified: 2023-08-31]