Question

Part A: Problem solving section 1. In last week homework students were determining the total hardness, carbonate hardness, non-carbonate hardness and the alkalinity of the following groundwater sample: Ca2+ = 94 mg/L Mg2+ = 24 mg/L Nat = 14 mg/L HCO3 = 317 mg/L SO42- = 67 mg/L Cl = 24 mg/L Build hardness bar chart and calculate the stoichiometric amount of lime and soda ash needed to soften this water sample.

Answer 1

Let's take the unit of hardness as

mg/L as CaCO3...
Lets take the unit of hardness as CaCO3) = (mgle as species Ew of Calo En of specie (mg/L as where EW - Equivalent weight Species - Ions, Radicals or compound T radicals. where EW - MW. - Electrical charge for radicals a Compounds EW = MW - for Valency ions. row - Molecular weight of species, 40 mg/mmole e 2 meg Immole = 20 mg/meg. Wat En each a 100 mg Immole = 50 mg lanea 2 meq Immole . [cat] mg/L as Calog = 94 * 50 straie (car = 235 mg/l as Cale 20

12.15 mg - Ewmght = 24.3 mg Immole = 2 meg Immole - [Mg2+] - 24 mgIL x. 50 ist - 98.765 mg/L as Caloz 12.15 Nat EW : 23.0 ng/meg 1 = 30.435 mg/l as Caloz HCO Ew = 61 mg/meg 317 50 [440s] = 317 x 50 = 259.836 mg/L as Calo, 61 o EW = 48 mg/meg 67 x 50 = 69.792 as mgle CaCO₃ 48 Enl = 35.5 mg/meg [ci]. • 24 mesos de 50 35.5 - 33.803 mg/L as CaCO3
Now we get the Hardness Bar Chart as..
& Hardness Bar Chart 235 4.7 li i Total hardness (TH) haha tit Eit Scale 50 : 1 ie, 235 Cations Cat Mg ²+1 Nat to w mglt ca la taken as a Anions HCO₃ SOAT 417 meq Ion concentration (meq/L)
Softening of hard water...
Softening of Hand water o Lime is added at the ratio of 1:1 for each Carbonate bardness Compound except for Mg(HCO₃) the ratio is 2:1 (ie 2 line for 1 Mg(HCO3)) Lime is also added at the ratio lil for each Magnesium NCH Compound (Here Masoq). • • ratio of 1:1 Soda for ash each is added Mg soa or at the CaSO4 of Here units meq IL or are either in the chemicals mg/L caca Therefore, according to our problem: For Carbonate Hardness softening we have a 4. 7 Ca(HCO3)₂ - 4. 7 lime 0.5 mg (14CO3) - 0.5x2= I line i 5.7 meq le of line For NCH softening 1.5 mg SO4 - I line & Soda augh
Therefore.

In total we need 6.7 meq/L of lime and 1meq/L of soda ash for softening the both carbonate and non carbonate hardness ie. The total hardness.

Hope you understand.. wish a bright study ahead..Convey your feedback..