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 Alkalinity of water, in equivalent/litre (eq/litre), is given by $\left\{\mathrm{HCO}_{3}^{-}\right\}+2\left\{\mathrm{CO}_{3}^{2-}\right\}+\left\{\mathrm{OH}^{-}\right\}-\left\{\mathrm{H}^{+}\right\}$ Where, \{\} represents concentration in mol/litre. For a water sample, the concentrations of $\mathrm{HCO}_{3}^{-}=2 \times 10^{-3} \mathrm{~mol} / \mathrm{litre}, \mathrm{CO}_{3}^{2-}=3.04 \times 10^{-4} \mathrm{~mol} /$ litre and the $\mathrm{pH}$ of water $=9.0 .$ The atomic weights are: $\mathrm{Ca}=40 ; \mathrm{C}=12 ;$ and $\mathrm{O}=16 .$ If the concentration of $\mathrm{OH}^{-}$ and $\mathrm{H}^{+}$ are NEGLECTED, the alkalinity of the water sample (in $\mathrm{mg} /$ litre as $\mathrm{CaCO}_{3}$ ), is
(A) 130.4
(B) 100.0
(C) 50.0
(D) 65.2



Question ID - 157421 | SaraNextGen Top Answer

 Alkalinity of water, in equivalent/litre (eq/litre), is given by $\left\{\mathrm{HCO}_{3}^{-}\right\}+2\left\{\mathrm{CO}_{3}^{2-}\right\}+\left\{\mathrm{OH}^{-}\right\}-\left\{\mathrm{H}^{+}\right\}$ Where, \{\} represents concentration in mol/litre. For a water sample, the concentrations of $\mathrm{HCO}_{3}^{-}=2 \times 10^{-3} \mathrm{~mol} / \mathrm{litre}, \mathrm{CO}_{3}^{2-}=3.04 \times 10^{-4} \mathrm{~mol} /$ litre and the $\mathrm{pH}$ of water $=9.0 .$ The atomic weights are: $\mathrm{Ca}=40 ; \mathrm{C}=12 ;$ and $\mathrm{O}=16 .$ If the concentration of $\mathrm{OH}^{-}$ and $\mathrm{H}^{+}$ are NEGLECTED, the alkalinity of the water sample (in $\mathrm{mg} /$ litre as $\mathrm{CaCO}_{3}$ ), is
(A) 130.4
(B) 100.0
(C) 50.0
(D) 65.2

1 Answer
127 votes
Answer Key / Explanation : (A) -

130.4

127 votes


127