Question

Que. A zeolite bed gets exhausted by
softening 2500 L of water sample and
requires 10 L of 5 % NaCl for
regeneration. Find the hardness of water
sample. ​

Answer 1

Explanation:

hope the above photo helps you with the answer

Answer 2

Given:

A zeolite bed gets exhausted by softening 2500 L of water sample

The process requires  10 L of 5 % NaCl for regeneration

To Find:

The hardness of the water sample

Solution:

The hardness of the water sample is 170 ppm.

5% of NaCl solution has 5g of sodium chloride dissolved in 100ml of water.

So in 1 L (1000ml), it will have 50g of NaCl.

The total amount of NaCl required for the regeneration process = 10 L of 5 % NaCl

= 10 X 50g

= 500g

From the reaction

CaCO₃ + Na₂Ze → 2 NaCl + CaZe

we know that 1 mole of CaCO₃ forms 2 moles of NaCl

or 100 g of CaCO₃ requires 2 X 58.5 g of NaCl

So 1 g of NaCl will react with 100 / 117 g of CaCO₃

So 500 g NaCl will react with 500 X 100 / 117

= 427.35 g

CaCO₃ present in 1 L of the water = 427.35 / 2500

= 0.17 g

= 170 mg

Hence the hardness of the water sample is 170 ppm.