Question

The molal elevation constant for water is $ 0.52 $ . What will be the boiling point of $2$ molar sucrose solution at $ 1atm $ pressure? (Assume B.P. of pure water as $ {{100}^{o}}C $ )

• A. $ {{101.04}^{o}}C $
• B. $ {{100.26}^{o}}C $
• C. $ {{100.52}^{o}}C $
• D. $ {{99.74}^{o}}C $

Answer 1

Answer: (A)

$\Delta T_{b}=k_{b} \times$ molality
for dilute solution
molarity = molarity $= 2$ (given)
and $k_b = 0.52$(given)
$\therefore \Delta T_b = 0.52 \times 2 = 1.04^{\circ} C$
Now,
$\Delta T_b = $B. P. of solution - B.P. pf $H_2O$
$= 1.04 + 100 = 101.04 ^{\circ} C$