The hardness of 85000 litres of water sample was removed by passing it through a zeolite softener. The zeolite required 2000 litres of NaCl solution containing 190 mg/lit of NaCl for regeneration. calculate the hardness of sample.

#### Solution

1 litres of NaCl solution = 190 mg of NaCl

∴ 2000 litres of NaCl = 2000 x 190 gm of NaCl

= 3,80,000 gm of NaCl.

Quantity of NaCl in terms of CaC0_{3} equivalent hardness.

= 3,80,000 xx 5/58.5 gm of CaC0_{3} equivalen,

= 3,24,786.3 gm ofCaC0_{3} equivalent

= 324.79 x10^{3} gm of CaC0_{3} equivalent

= 324.79 x10^{6 }gm of CaC0_{3} equivalent

Hardness of 85000 litres of water = 324. 79x10^{6} gm

∴ Hardness of 1 litre = `(324.79 xx 10^6)/85000 3821` mg/litre

∴ Hardness of water = 3821 mg/lit

= 3821 ppm.