Hardness in water Flashcards
1
Q
What is hard water?
A
Any water that forms a scum with soap.
Does not form a lather with soap.
2
Q
What is soft water?
A
Forms a lather with soap.
3
Q
How is scum formed?
A
Soap is sodium stearate.
Calcium or magnesium ions in the water react with stearate ions in the soap to form insoluble scum- calcium stearate or magnesium stearate.
4
Q
How do calcium ions get in the water?
A
Carbon dioxide in the air reacts with water to form carbonic acid.
CO2 + H2O = H2CO3
Reacts with limestone to form calcium hydrogen carbonate:
CaCO3 + H2CO3= Ca(HCO3)2.
5
Q
What are the two types of hardness.
A
Temporary hardness.
Permanent hardness.
