Choose the incorrect statement:

Correct option is B

Statement 2 is incorrect because carbon dioxide (CO₂) is soluble in boiling water. However, the solubility decreases with increasing temperature. At boiling temperature (100°C), CO₂ still dissolves, albeit in very small amounts.
Correct Analysis of Other Statements:
1. O₂ dissolved in surface water does not react chemically with water molecules
· This statement is correct. Dissolved oxygen in water remains in its molecular form and does not chemically react under normal conditions.
2. Removal of CO₂ increases pH of water and changes alkalinity from carbonate to hydroxide
· This is correct. Removing CO₂ reduces carbonic acid concentration, raising the pH and shifting alkalinity to hydroxide ions.
3. Addition of CO₂ in water increases CaCO₃ formation and precipitation
· Correct. CO₂ dissolves in water to form carbonic acid, which reacts with calcium ions to precipitate calcium carbonate ( CaCO₃).
Information Booster:
1. Solubility of CO₂:
· Solubility decreases with temperature. At 0°C, CO₂ solubility is high; at 100°C, it is minimal but not zero.
2. Carbonate System in Water:
· CO₂ + H₂O ⇌ H₂CO₃ (carbonic acid)
· Carbonic acid dissociates to bicarbonate (HCO₃⁻) and carbonate (CO₃²⁻) ions, influencing pH and alkalinity.
3. Dissolved Oxygen (DO):
· Essential for aquatic life. Dissolved oxygen levels depend on temperature and pressure.
4. Effect of CO₂ on pH:
· Adding CO₂ lowers pH (more acidic).
· Removing CO₂ raises pH (more basic).
5. Calcium Carbonate Precipitation:
· Important in water treatment and natural processes (e.g., cave formation, scaling in pipes).
Additional Knowledge:
· Boiling Water and Gas Solubility:
· As water heats up to 100°C, gases like CO₂ and O₂ become less soluble because the kinetic energy of gas molecules increases, facilitating their escape from the liquid.
· Alkalinity Shifts:
· High pH: Dominated by hydroxide ions (OH⁻).
· Low pH: Dominated by carbonic acid and bicarbonate ions.
· Water Chemistry:
· Balancing CO₂ levels is crucial for maintaining water quality, especially in aquariums, water treatment, and natural water bodies.