Question

Water sample on analysis gave the following data:- CaCO3= 75 ppm, , Mg(HCO3)2= 73 ppm CaCl2= 166.5 ppm, MgCl2= 190 ppm, MgSO4= 30 ppm, CO2 = 10 ppm. Calculate:- 1.Temporary and Permanent Hardness. 2. Quantities of lime (90% pure) and soda (95% pure) required for softening of 1,00,000 litres of water using NaAlO2 as a coagulant at the rate of 8.2 mg/lit. 3. If 10, 000 lit of this water is passed through zeolite softner, it requires 100 litres of NaCl solution for regeneration. Find concentration of NaCl. *

Answer 1

Explanation:

mole of Ca(HCO3)2 = (162 g/mole)/162×10-³mg ,= 1×10−3 moles

Mole of Ca(SO)4 = (136g/mole)/(136×10-3g) = 1×10-3 mole

Total mole of Ca=2×10 −3 mole

mass of CaCO3 = 2×10 −3 ×100=0.2g

∴ ppm (permanent hardness) = 6.2/1000 × 10^6 =200ppm

Mole of MgCl 2 = 95 ×10 −3g = 1×10 −3 mole

Mole Mg (HCO3) 2 = 146/73×10 −3 = 5 ×10-4 mole

mole Mg =1.5×10 −4 mole

Mole CaCO 3v= 1.5×10 −3

mass =1.5×10 −3

=0.150g

ppm (temporary hardness) = 100× 0.150×106=150ppm