A solution of urea (mol. mass .56 ~g ~mol ⁻¹ ) boils at 100.18^ C at the atmospheric pressure. If K _f and K _b for water for 1.86 and 0.512 Kkmol ⁻¹ respectively, the above solution will freeze at:

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Correct answer: B. -0.654^ C

aligned T _f & = K _f m (1) T _b & = K _b m (2) T _f T _b & = K _f ~K _b (3) aligned aligned & b.p. of water =100^ C ; K _f=1.86 ~kg & ~mol ⁻¹ & b.p. of urea in water =100.18^ C ; K _b & =0.512 ~kg ~mol ⁻ & T _b=0.18 & f.p. of water =0^ C & f . p . of urea in water =- T ^ C & T _f= T & from eq. (3) & T 0.18 = 1.86 0.512 & T =0.6539 & f . p . of urea in water =-0.654^ C aligned

A solution of urea (mol. mass .56 ~g ~mol ⁻¹ ) boils at 100.18^ C at the atmospheric pressure. If K _f and K _b for water for 1.86 and 0.512 Kkmol ⁻¹ respectively, the above solution will freeze at:

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