Water Hardness Quiz

Water Hardness

• Hardness is caused by soluble salts of calcium and magnesium
• Soluble salts include calcium chloride and magnesium sulphate
• Nitrate is soluble, while phosphate is insoluble
• Only cations cause hardness, never anions
• Specifications for drinking water include no shell, clear and transparent, suspended impurities, and TDS - 200 ppm

Types of Hardness

• Temporary Hardness: Caused by soluble bicarbonate salts of calcium and magnesium
• These salts decompose when heated
• Decomposing releases carbon dioxide, forming insoluble carbonates
• Permanent Hardness: Caused by soluble sulphate and chloride salts of calcium and magnesium
• These salts do not decompose when heated, retaining their hardness

Determination of Hardness (EDTA Method)

• EDTA (ethylenediaminetetraacetic acid) is used to determine hardness in water
• Disodium salt of EDTA is preferred due to higher purity
• The method involves titration with a standard EDTA solution and an indicator
• The indicator EBT (Eriochrome Black T) changes color upon reaching the end point

Why CaCO₃ is the Standard

• CaCO₃ is chosen due to its low molecular weight, facilitating calculations
• During water softening, other hardness causing salts precipitate, which is taken into account in calculations using a standard

Units of Hardness

• Parts per million (ppm)
• Milligrams per liter (mg/L)
• The values are equivalent (ppm=mg/L)

Boiler Feed Water

• Boiler scales and sludges
• Boiler corrosion
• Acoustic embrittlement
• Priming and foaming

Removal of Hardness

• Chemical treatment
• Zeolite softner method
• Lime soda process

Water Softening Methods

• External treatment (Treating water before adding)
• Internal treatment (Treating water with chemicals after adding)
• Zeolite process
• Lime soda process

Disinfection/Sterilisation

• Making water free from pathogenic bacteria
• Chlorination, UV Treatment, Ozone treatment, and Potassium permanganate treatment
• Chlorination is considered the most effective method but can lead to a foul odor if not used at appropriate concentrations

Other Methods of Disinfection

• Ozone treatment and UV treatment

Test your knowledge on water hardness, including its causes, types, and methods of determination. This quiz covers both temporary and permanent hardness, and the use of EDTA in titration methods. Perfect for students studying environmental science.