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(a) When 2.56 g of sulphur was dissolved in 100 g of CS_{2}, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (S_{X})

(K_{f} for CS_{2}=3.83\; K\; kg\; mol^{-1} Atomic mass of sulphur =32\; g\; mol^{-1})

(b) Blood cells are isotonic with 0.9\; ^{o}/_{o} sodium chloride solution. What happens if we place blood cells in a solution containing ?

(i) 1.2\; ^{o}/_{o} sodium chloride solution

(ii) 0.4\; ^{o}/_{o} sodium chloride solution

 

 

 

 
 
 
 
 

Answers (1)

(a) K_{f}(CS_{2})=3.83\; K\; kg\; mol^{-1}

        Atomic mass of sulphur =32\; g\; mol^{-1}

        Mass of sulphur =2.56\; g

        Mass of CS_{2}=100 \; g

        \Delta T_{f}=0.383 \; K

        Formula of sulphur (S_{X}), \; X=?

      \Delta T_{f}=l\times K_{f}\times m

       0.383=i\times 3.83\times \frac{2.56\times 1000}{32\times 100}

        i=\frac{0.383\times 32\times 100}{3.83\times 2.56\times 1000}

        i=\frac{1}{8}

    \therefore \; X=8

Formula of sulphur =S_{8}

(b) Blood cells are isotonic with 0.9\; ^{o}/_{o}\; NaCl solution . If we place blood cells in -

(i) 1.2\; ^{o}/_{o}\; NaCl solution blood cells will shrink.

(ii) 0.4\; ^{o}/_{o}\; NaCl solution 

       blood cells will swell.  

Posted by

Sumit Saini

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