Question

4) Calculate the lime and soda required to soften 10,000 liters of water sample having.
Calcium hardness = 450 mg/l as CaCO3
Magnesium hardness = 15 mg/l as CaCO3
And total hardness = 400 mg/l as CaCO3​

Answer 1

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Explanation:

Answer 2

Given : Volume of water sample

= 10,000

Calcium hardness = 450 mg/l CaCO3

Magnesium hardness = 15 mg/l as CaCO3

And Total hardness = 400 mg/l as CaCO3

To Find: Amount of lime and soda required

Solution:

- Water can be hard or soft. Moreover, Hard water can be made soft by adding lime and soda.

- Water became hard due to presence of the constituents like Magnesium carbonate, calcium carbonate, calcium chloride, magnesium chloride.

- The formula for the calculation of lime and soda to provide softness to water is given below:-

Lime required for softening

= 74/100[CaCO3 + 2× MgCO3 + MgCl2 as CaCO3 eq] × vol. of water.

- Total hardness = Hardness of CaCO3 + MgCO3 +MgCl2

- Given that ,Total hardness is 400mg/l

400 = 450 + 15 + MgCl2

400 - 465 = MgCl2

So, the hardness of MgCl2 is - 65mg/l as CaCO3

- By putting the values in the formula,

Lime required for softening

= 74/100[450 + 2 ×15 + (-65)] × 10,000

= 74/100[415]×10,000

= 3,071,000mg

= or 3071kg of lime

- Sode required for softening

= 106/100[CaCO3 + 2× MgCO3 + MgCl2 as CaCO3 eq] × vol. of water.

= 106/100[450 + 2 ×15 + (-65)] × 10,000

= 106/100[415]×10,000

= 4,399,000mg

= 4,399kg

- So, The required lime and soda for softening of water are 3071kg and 4399kg.