KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    100 mL of a water sample contains 0.81 g of calcium bicarbonate and 0.73 g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalents of \[CaC{{O}_{3}}\] is: (molar mass of calcium bicarbonate is \[162\,g\,\,mo{{l}^{-\,1}}\]  and magnesium bicarbonate is \[146\text{ }g\text{ }mo{{l}^{-1}}\])

    A) 100 ppm                       

    B) 1,000 ppm

    C) 5,000 ppm                    

    D) 10,000 ppm

    Correct Answer: D

    Solution :

    Ppm of \[CaC{{O}_{3}}=?\]
    Degree of hardness \[=\frac{weight\,\,of\,hardness\,\,cau\sin g\,\,salt}{Mw}\times 100\]
    1 ppm=1 part \[CaC{{O}_{3}}\] eq in \[{{10}^{6}}\]parts water \[ppm\,\,of\,\,CaC{{O}_{3}}=\,\frac{\left( \frac{0.73}{146}+\frac{0.81}{162} \right)\times 100}{100}\times {{10}^{6}}\]\[={{10}^{4}}ppm\]

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