Question

Why is the pH of distilled water usually < 7?

Dissolved fluorine from the atmosphere lowers the pH by reacting with water to form hydrofluoric acid.Dissolved CO₂ from the atmosphere lowers the pH by reacting with water to form carbonic acid.    Dissolved NO₂ from the atmosphere lowers the pH by reacting with water to form nitric acid.Dissolved CO from the atmosphere lowers the pH by reacting with water to form carbonic acid.

How can you prevent this from happening? (Select all that apply.)

Most CO can be removed by boiling the distilled water.Water can be distilled under an inert atmosphere to exclude CO.Water can be distilled under an inert atmosphere to exclude CO₂.Most NO₂ can be removed by boiling the distilled water.Most CO₂ can be removed by boiling the distilled water.Water can be distilled under an inert atmosphere to exclude CO.Most fluorine can be removed by boiling the distilled water.Water can be distilled under an inert atmosphere to exclude CO.

Answer 1

Why is the pH of distilled water usually < 7?

Dissolved fluorine from the atmosphere lowers the pH by reacting with water to form hydrofluoric acid.

Dissolved CO₂ from the atmosphere lowers the pH by reacting with water to form carbonic acid.   

Dissolved NO₂ from the atmosphere lowers the pH by reacting with water to form nitric acid.

Dissolved CO from the atmosphere lowers the pH by reacting with water to form carbonic acid.

The p H of distilled water is less than 7 means it is slightly acidic because   Dissolved CO₂ from the atmosphere lowers the pH by reacting with water to form carbonic acid

H2O + CO2 = H2CO3

H2CO3 < = > H+ + HCO3-