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# Boiling point of water at 750 mm Hg is 99.63 degree C. How much sucrose is to be added to 500 g of water such that it boils at 100 degree C.

2.10    Boiling point of water at $\inline 750 \; mm \; Hg$  is  $\inline 99.63^{\circ}C$. How much sucrose is to be added to $\inline 500 \; g$ of water such that it boils at $\inline 100^{\circ}C.$

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Here we will use the formula :

$\Delta T_b = \frac{K_b\times1000\times w_2}{M_2\times w_1}$

Elevation in temperature =  100 -  99.63  =  0.37

Kb = 0.52 ;     $Molar\ mass\ of\ sucrose = 11(12) + 22(1) + 11(16) = 342\ g\ mol^{-1}$

Putting all values in above formula, we get :

$w_2 = \frac{0.37\times342\times500}{0.52\times1000}= 121.67\ g$

Thus 121.67 g of sucrose needs to be added.

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