Softening of hard water

Identify water softening methods from following

• Reverse Osmosis

• Deionisation

• Zeolite method

• electrodialysis

• activated sludge

In lime soda method the principle is ----

• Convert soluble salt into insoluble precipitate

• substitute cations and anions of hardness producing salts

• replace cations by Na+

• none of the above

Anion Exchange and Cation Exchange resins are part of (a)   process.

In an ion exchange process, ions removed from the water are exchanged with ions of _____________ from the resin's surface.

• Similar charge (+ ,+)

• Opposite charge (+, -)

Water softened by Deionisation process has residual hardness as --

• >50 ppm

• > 10 ppm

• < 2 ppm

• 100 ppm

Advantages of ion exchange process are

• Highly acidic and basic water can be treated

• no sludge formation

• cost effective method

• compact

• skilled supervisor required

Disadvantage of Ion exchange process is --

• Costly

• more residual hardness

• Difficult to operate

• Turbidity and suspended particles can block the resin pores

Once the water softening is done, we need to throw resins.

• TRUE

• FALSE

In regeneration of cation exchange resin ----is used

• HCl, H2SO4 etc

• NaOH, KOH etc

• NaCl, Na2SO4 etc

• Alcohols

Calcium and magnesium are replaced by ----

and Sulphates, Nitrates and chlorides are replaced by ---respectively

(a)