q. ca2 20 ppm mg2 25 ppm co2 30 ppm hco-3

Question

Q. Ca⁺² = 20 ppm, Mg⁺² = 25 ppm, CO₂ = 30 ppm, HCO^-₃ = 150, K⁺ = 10 ppm. Calculate the lime (87% pure) and soda (91% pure) required softening 1 million litters of water sample.

Ans.

Calculation of CaCO₃ equivalent of given impurities:

S.NO	substances	Amount of substances in mg/L	Multiplication factor	CaCO3 equivalent mg/L
1.	Ca++	20 ppm	100/40	100/40*20 =50
2.	Mg++	25 ppm	100/24	100/24*25 = 104.16
3.	CO2	30 ppm	100/44	100/44*30  = 68.181
4.	HCO-3	150 ppm	100/122	100/122*150 = 122.95
5.	K+	10 ppm	Not produce hardness

Lime required:

74/100[Mg⁺⁺ + CO₂ + HCO^-₃ as CaCO₃ equivalent] mg/L *Volume of water*100/%purity

74/100[104.16 + 68.181 + 122.95] mg/L*1000000l*100/86

74/100[295.29] mg/L * 100000*100/87

= 251.16*10⁶ mg

= 251.16*10⁶ mg*1Kg/10⁶

= 251.16

Soda required = 106/100[50 + 104.16 – 122.95] mg/L *1000000*100/91

   = 100/106[31.21] mg/L*106*100/91

   = 36.35*10⁶ mg

   = 36.35*10⁶ mg*1Kg/10⁶

    = 36.35Kg