3. (15 points) Choose the answer from the followings. A sample of water has the

Question

3. (15 points) Choose the answer from the followings. A sample of water has the following concentration of ions (and the PH is near neutra): Cations Ca Mg2 Na mg/L 95.0 26.0 15.0 Anions HCO3 SO4 Ch mg/L 160.0 135.0 73.0 (MW: calcium 40, magnesium-24, sodium-23, carbon 12, oxygen 16, sulfur 32, chloride-35.5, hydrogen-1) a) (5 points) What is the total hardness (meq/L)? 1. 6.88 meq/L 2. 2.32 meq/L 3. 344.1 meq/L 4. 125.5 meq/L b) (5 points) What is the carbonate hardness (meq/L)? 1. 6.88 meq/L 2. 2.62 meq/L 3.4.32 meq/L 4. 131.1 meq/L c) (5 points) What is the total dissolved solids concentration (mg/L)? 1. 405 mg/L 2. 380 mg/L 3. 180 mg/L 4. 504 mg/l

Explanation / Answer

a)

Total hardness of water is a measure of the quantity of divalent or all multivalent cations.

water hardness (mg/L) = Ca (mg/L) x 2.497 + Mg (mg/L) x 4.118

= 344.28 mg/L of CaCO3

b)

carboante hardness = HCO3 (mg/L) x 0.82

= 160 x 0.82

= 131.2 mg/L as CaCO3

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