Question

1000 kg of hard water contains 48 ppm of SO2−4 and 183 ppm of HCO−3 as well as Ca2+ ion. What is the degree of hardness of the above sample of water?
A
200 ppm
B
100 ppm
C
2000 ppm
D
1000 ppm

Answer 1

Answer:

Sample of hard water contains 96 ppm SO42− and 40 ppm Ca2+(CaSO4). 

Also, it contains 183 ppm HCO3− and 60 ppm Ca2+[Ca(HCO3)2].

To remove Ca(HCO3)2 from 103 kg or 106 g sample of hard water which contains 243 g Ca(HCO3)2 or 23 moles of Ca(HCO3)2, CaO required is 23 moles.

Ca(HCO3)2+CaO→CaCO3+H2O+CO2

Thus, moles of CaO required =23 or 1.5

Also, Ca2+ ions left in solution are of CaSO4 

SO CORRECT OPTION IS OPTION A