# 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 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

• Problem. Titration of HCl with NaOH.
• Problem. Carbonate Species vs. pH – Closed System
• Problem. Carbonate Species vs. pH – Open System

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

• Problem. Dissolution of Calcite in a closed and in an open CO2 system
• Problem. Dissolution of Gypsum
• Problem. Temperature dependence of calcite precipitation

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?