Unit 3: 2 - Hard Water Flashcards
What does hard water produce when exposed to soap? Why?
Scum. Metal ions in the water react with the soap to make scum.
What water lathers easily with soap?
Soft
Which ions make water hard?
Calcium and Magnesium ions.
Where do the ions in hard water come from?
The ground as it filters through. Different areas have different minerals in the ground.
How is scale formed?
By heating a certain type of hard water.
Why is scale a problem?
It is insoluble and it reduces the efficiency of heating systems. It also causes blockages.
Give some health benefits of hard water.
- Good calcium content for teeth and bones
- Calcium may reduce the risk of heart disease.
Give an industrial benefit of hard water.
Some brewers prefer the taste.
Give the 2 types of hard water.
Temporary hard water and Permanent hard water.
Which type of hard water causes scale?
Temporary hard water.
Which water is not softened by boiling?
Permanent hard water.
How is temporary hard water softened by heating?
It contains hydrogencarbonate ions, HCO3 (aq). These ions decompose when heated to produce carbonate ions, water and CO2.
Give a symbol and word equation of temporary hard water being softened by heating.
2HCO3- (aq) –> CO3 2- (aq) + H2O (l) + CO2 (g)
Hydrogrencarbonate –> Carbonate ions + Water + Carbon dioxide.
Give a method of softening either type of hard water. (precip)
Precipitating out the ions which cause hardness, using washing soda.
What is washing soda?
Sodium carbonate
