The hardness of a  water sample (in terms of equivalents of CaCO_{3}) containing  10^{-3}M \: CaSO_{4} is :

(molar mass of CaSO_{4}=136\: g\: mol^{-1})

  • Option 1)

    10 ppm

  • Option 2)

    90 ppm

  • Option 3)

    100 ppm

  • Option 4)

    50 ppm

Answers (1)
A admin

 

Molar Mass -

The mass of one mole of a substance in grams is called its molar mass.

- wherein

 Molar mass of water = 18 g mol-1

 

 

Hardness is most commonly expressed as milligrams of calcium carbonate equivalent per litre. Water containing calcium carbonate at concentrations below 60 mg/l is generally considered as soft; 60–120 mg/l 

as we learn

in equlibrium

initialA+2B\rightleftharpoons 2C+D

         a       1,5a

at eg. a-x1.5\left ( a-2x \right )2_{x}

at eg a-x= 1.5_{a}-2x

0.5_{a}= xa= 2x

K_{c}= \frac{\left ( 2x \right )^{2}\left ( x \right )}{\left ( a-x \right )\left ( 1.5a-2x \right )^{2}}= \frac{4x^{2}x}{\left ( x \right )\left ( x \right )^{2}}= 4

 


Option 1)

10 ppm

Option 2)

90 ppm

Option 3)

100 ppm

Option 4)

50 ppm

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